API

这部分文档涵盖了 Flask 的所有接口。对于那些 Flask 依赖外部库的部分，我们 这里提供了最重要的部分的文档，并且提供其官方文档的链接。

应用对象

class flask.Flask(import_name, static_path=None, static_url_path=None, static_folder='static', template_folder='templates', instance_path=None, instance_relative_config=False)

The flask object implements a WSGI application and acts as the central object. It is passed the name of the module or package of the application. Once it is created it will act as a central registry for the view functions, the URL rules, template configuration and much more.

The name of the package is used to resolve resources from inside the package or the folder the module is contained in depending on if the package parameter resolves to an actual python package (a folder with an __init__.py file inside) or a standard module (just a .py file).

For more information about resource loading, see open_resource().

Usually you create a Flask instance in your main module or in the __init__.py file of your package like this:

from flask import Flask
app = Flask(__name__)

About the First Parameter

The idea of the first parameter is to give Flask an idea what belongs to your application. This name is used to find resources on the file system, can be used by extensions to improve debugging information and a lot more.

So it’s important what you provide there. If you are using a single module, __name__ is always the correct value. If you however are using a package, it’s usually recommended to hardcode the name of your package there.

For example if your application is defined in yourapplication/app.py you should create it with one of the two versions below:

app = Flask('yourapplication')
app = Flask(__name__.split('.')[0])

Why is that? The application will work even with __name__, thanks to how resources are looked up. However it will make debugging more painful. Certain extensions can make assumptions based on the import name of your application. For example the Flask-SQLAlchemy extension will look for the code in your application that triggered an SQL query in debug mode. If the import name is not properly set up, that debugging information is lost. (For example it would only pick up SQL queries in yourapplication.app and not yourapplication.views.frontend)

0.7 新版功能: The static_url_path, static_folder, and template_folder parameters were added.

0.8 新版功能: The instance_path and instance_relative_config parameters were added.

参数:

• import_name – the name of the application package
• static_url_path – can be used to specify a different path for the static files on the web. Defaults to the name of the static_folder folder.
• static_folder – the folder with static files that should be served at static_url_path. Defaults to the 'static' folder in the root path of the application.
• template_folder – the folder that contains the templates that should be used by the application. Defaults to 'templates' folder in the root path of the application.
• instance_path – An alternative instance path for the application. By default the folder 'instance' next to the package or module is assumed to be the instance path.
• instance_relative_config – if set to True relative filenames for loading the config are assumed to be relative to the instance path instead of the application root.

add_template_filter(*args, **kwargs)

Register a custom template filter. Works exactly like the template_filter() decorator.

参数:name – the optional name of the filter, otherwise the function name will be used.

add_template_global(*args, **kwargs)

Register a custom template global function. Works exactly like the template_global() decorator.

0.10 新版功能.

参数:name – the optional name of the global function, otherwise the function name will be used.

add_template_test(*args, **kwargs)

Register a custom template test. Works exactly like the template_test() decorator.

0.10 新版功能.

参数:name – the optional name of the test, otherwise the function name will be used.

add_url_rule(*args, **kwargs)

Connects a URL rule. Works exactly like the route() decorator. If a view_func is provided it will be registered with the endpoint.

Basically this example:

@app.route('/')
def index():
    pass

Is equivalent to the following:

def index():
    pass
app.add_url_rule('/', 'index', index)

If the view_func is not provided you will need to connect the endpoint to a view function like so:

app.view_functions['index'] = index

Internally route() invokes add_url_rule() so if you want to customize the behavior via subclassing you only need to change this method.

For more information refer to URL 路由注册.

在 0.2 版更改: view_func parameter added.

在 0.6 版更改: OPTIONS is added automatically as method.

参数:

• rule – the URL rule as string
• endpoint – the endpoint for the registered URL rule. Flask itself assumes the name of the view function as endpoint
• view_func – the function to call when serving a request to the provided endpoint
• options – the options to be forwarded to the underlying Rule object. A change to Werkzeug is handling of method options. methods is a list of methods this rule should be limited to (GET, POST etc.). By default a rule just listens for GET (and implicitly HEAD). Starting with Flask 0.6, OPTIONS is implicitly added and handled by the standard request handling.

after_request(*args, **kwargs)

Register a function to be run after each request. Your function must take one parameter, a response_class object and return a new response object or the same (see process_response()).

As of Flask 0.7 this function might not be executed at the end of the request in case an unhandled exception occurred.

after_request_funcs = None

A dictionary with lists of functions that should be called after each request. The key of the dictionary is the name of the blueprint this function is active for, None for all requests. This can for example be used to open database connections or getting hold of the currently logged in user. To register a function here, use the after_request() decorator.

app_context()

Binds the application only. For as long as the application is bound to the current context the flask.current_app points to that application. An application context is automatically created when a request context is pushed if necessary.

Example usage:

with app.app_context():
    ...

0.9 新版功能.

app_ctx_globals_class

The class that is used for the g instance.

Example use cases for a custom class:

1. Store arbitrary attributes on flask.g.
2. Add a property for lazy per-request database connectors.
3. Return None instead of AttributeError on expected attributes.
4. Raise exception if an unexpected attr is set, a “controlled” flask.g.

In Flask 0.9 this property was called request_globals_class but it was changed in 0.10 to app_ctx_globals_class because the flask.g object is not application context scoped.

0.10 新版功能.

_AppCtxGlobals 的别名

auto_find_instance_path()

Tries to locate the instance path if it was not provided to the constructor of the application class. It will basically calculate the path to a folder named instance next to your main file or the package.

0.8 新版功能.

before_first_request(*args, **kwargs)

Registers a function to be run before the first request to this instance of the application.

0.8 新版功能.

before_first_request_funcs = None

A lists of functions that should be called at the beginning of the first request to this instance. To register a function here, use the before_first_request() decorator.

0.8 新版功能.

before_request(*args, **kwargs)

Registers a function to run before each request.

before_request_funcs = None

A dictionary with lists of functions that should be called at the beginning of the request. The key of the dictionary is the name of the blueprint this function is active for, None for all requests. This can for example be used to open database connections or getting hold of the currently logged in user. To register a function here, use the before_request() decorator.

blueprints = None

all the attached blueprints in a dictionary by name. Blueprints can be attached multiple times so this dictionary does not tell you how often they got attached.

0.7 新版功能.

config = None

The configuration dictionary as Config. This behaves exactly like a regular dictionary but supports additional methods to load a config from files.

context_processor(*args, **kwargs)

Registers a template context processor function.

create_global_jinja_loader()

Creates the loader for the Jinja2 environment. Can be used to override just the loader and keeping the rest unchanged. It’s discouraged to override this function. Instead one should override the jinja_loader() function instead.

The global loader dispatches between the loaders of the application and the individual blueprints.

0.7 新版功能.

create_jinja_environment()

Creates the Jinja2 environment based on jinja_options and select_jinja_autoescape(). Since 0.7 this also adds the Jinja2 globals and filters after initialization. Override this function to customize the behavior.

0.5 新版功能.

create_url_adapter(request)

Creates a URL adapter for the given request. The URL adapter is created at a point where the request context is not yet set up so the request is passed explicitly.

0.6 新版功能.

在 0.9 版更改: This can now also be called without a request object when the URL adapter is created for the application context.

debug

The debug flag. Set this to True to enable debugging of the application. In debug mode the debugger will kick in when an unhandled exception occurs and the integrated server will automatically reload the application if changes in the code are detected.

This attribute can also be configured from the config with the DEBUG configuration key. Defaults to False.

debug_log_format = '--------------------------------------------------------------------------------\n%(levelname)s in %(module)s [%(pathname)s:%(lineno)d]:\n%(message)s\n--------------------------------------------------------------------------------'

The logging format used for the debug logger. This is only used when the application is in debug mode, otherwise the attached logging handler does the formatting.

0.3 新版功能.

default_config = ImmutableDict({'JSON_AS_ASCII': True, 'USE_X_SENDFILE': False, 'SESSION_COOKIE_PATH': None, 'SESSION_COOKIE_DOMAIN': None, 'SESSION_COOKIE_NAME': 'session', 'LOGGER_NAME': None, 'DEBUG': False, 'SECRET_KEY': None, 'MAX_CONTENT_LENGTH': None, 'APPLICATION_ROOT': None, 'SERVER_NAME': None, 'PREFERRED_URL_SCHEME': 'http', 'JSONIFY_PRETTYPRINT_REGULAR': True, 'TESTING': False, 'PERMANENT_SESSION_LIFETIME': datetime.timedelta(31), 'PROPAGATE_EXCEPTIONS': None, 'TRAP_BAD_REQUEST_ERRORS': False, 'JSON_SORT_KEYS': True, 'SESSION_COOKIE_HTTPONLY': True, 'SEND_FILE_MAX_AGE_DEFAULT': 43200, 'PRESERVE_CONTEXT_ON_EXCEPTION': None, 'SESSION_COOKIE_SECURE': False, 'TRAP_HTTP_EXCEPTIONS': False})

Default configuration parameters.

dispatch_request()

Does the request dispatching. Matches the URL and returns the return value of the view or error handler. This does not have to be a response object. In order to convert the return value to a proper response object, call make_response().

在 0.7 版更改: This no longer does the exception handling, this code was moved to the new full_dispatch_request().

do_teardown_appcontext(exc=None)

Called when an application context is popped. This works pretty much the same as do_teardown_request() but for the application context.

0.9 新版功能.

do_teardown_request(exc=None)

Called after the actual request dispatching and will call every as teardown_request() decorated function. This is not actually called by the Flask object itself but is always triggered when the request context is popped. That way we have a tighter control over certain resources under testing environments.

在 0.9 版更改: Added the exc argument. Previously this was always using the current exception information.

enable_modules = True

Enable the deprecated module support? This is active by default in 0.7 but will be changed to False in 0.8. With Flask 1.0 modules will be removed in favor of Blueprints

endpoint(*args, **kwargs)

A decorator to register a function as an endpoint. Example:

@app.endpoint('example.endpoint')
def example():
    return "example"

参数:endpoint – the name of the endpoint

error_handler_spec = None

A dictionary of all registered error handlers. The key is None for error handlers active on the application, otherwise the key is the name of the blueprint. Each key points to another dictionary where they key is the status code of the http exception. The special key None points to a list of tuples where the first item is the class for the instance check and the second the error handler function.

To register a error handler, use the errorhandler() decorator.

errorhandler(*args, **kwargs)

A decorator that is used to register a function give a given error code. Example:

@app.errorhandler(404)
def page_not_found(error):
    return 'This page does not exist', 404

You can also register handlers for arbitrary exceptions:

@app.errorhandler(DatabaseError)
def special_exception_handler(error):
    return 'Database connection failed', 500

You can also register a function as error handler without using the errorhandler() decorator. The following example is equivalent to the one above:

def page_not_found(error):
    return 'This page does not exist', 404
app.error_handler_spec[None][404] = page_not_found

Setting error handlers via assignments to error_handler_spec however is discouraged as it requires fiddling with nested dictionaries and the special case for arbitrary exception types.

The first None refers to the active blueprint. If the error handler should be application wide None shall be used.

0.7 新版功能: One can now additionally also register custom exception types that do not necessarily have to be a subclass of the HTTPException class.

参数:code – the code as integer for the handler

extensions = None

a place where extensions can store application specific state. For example this is where an extension could store database engines and similar things. For backwards compatibility extensions should register themselves like this:

if not hasattr(app, 'extensions'):
    app.extensions = {}
app.extensions['extensionname'] = SomeObject()

The key must match the name of the flaskext module. For example in case of a “Flask-Foo” extension in flaskext.foo, the key would be 'foo'.

0.7 新版功能.

full_dispatch_request()

Dispatches the request and on top of that performs request pre and postprocessing as well as HTTP exception catching and error handling.

0.7 新版功能.

get_send_file_max_age(filename)

Provides default cache_timeout for the send_file() functions.

By default, this function returns SEND_FILE_MAX_AGE_DEFAULT from the configuration of current_app.

Static file functions such as send_from_directory() use this function, and send_file() calls this function on current_app when the given cache_timeout is None. If a cache_timeout is given in send_file(), that timeout is used; otherwise, this method is called.

This allows subclasses to change the behavior when sending files based on the filename. For example, to set the cache timeout for .js files to 60 seconds:

class MyFlask(flask.Flask):
    def get_send_file_max_age(self, name):
        if name.lower().endswith('.js'):
            return 60
        return flask.Flask.get_send_file_max_age(self, name)

0.9 新版功能.

got_first_request

This attribute is set to True if the application started handling the first request.

0.8 新版功能.

handle_exception(e)

Default exception handling that kicks in when an exception occurs that is not caught. In debug mode the exception will be re-raised immediately, otherwise it is logged and the handler for a 500 internal server error is used. If no such handler exists, a default 500 internal server error message is displayed.

0.3 新版功能.

handle_http_exception(e)

Handles an HTTP exception. By default this will invoke the registered error handlers and fall back to returning the exception as response.

0.3 新版功能.

handle_url_build_error(error, endpoint, values)

Handle BuildError on url_for().

handle_user_exception(e)

This method is called whenever an exception occurs that should be handled. A special case are HTTPExceptions which are forwarded by this function to the handle_http_exception() method. This function will either return a response value or reraise the exception with the same traceback.

0.7 新版功能.

has_static_folder

This is True if the package bound object’s container has a folder named 'static'.

0.5 新版功能.

init_jinja_globals()

Deprecated. Used to initialize the Jinja2 globals.

0.5 新版功能.

在 0.7 版更改: This method is deprecated with 0.7. Override create_jinja_environment() instead.

inject_url_defaults(endpoint, values)

Injects the URL defaults for the given endpoint directly into the values dictionary passed. This is used internally and automatically called on URL building.

0.7 新版功能.

instance_path = None

Holds the path to the instance folder.

0.8 新版功能.

jinja_env

The Jinja2 environment used to load templates.

jinja_loader

The Jinja loader for this package bound object.

0.5 新版功能.

jinja_options = ImmutableDict({'extensions': ['jinja2.ext.autoescape', 'jinja2.ext.with_']})

Options that are passed directly to the Jinja2 environment.

json_decoder

The JSON decoder class to use. Defaults to JSONDecoder.

0.10 新版功能.

JSONDecoder 的别名

json_encoder

The JSON encoder class to use. Defaults to JSONEncoder.

0.10 新版功能.

JSONEncoder 的别名

log_exception(exc_info)

Logs an exception. This is called by handle_exception() if debugging is disabled and right before the handler is called. The default implementation logs the exception as error on the logger.

0.8 新版功能.

logger

A logging.Logger object for this application. The default configuration is to log to stderr if the application is in debug mode. This logger can be used to (surprise) log messages. Here some examples:

app.logger.debug('A value for debugging')
app.logger.warning('A warning occurred (%d apples)', 42)
app.logger.error('An error occurred')

0.3 新版功能.

logger_name

The name of the logger to use. By default the logger name is the package name passed to the constructor.

0.4 新版功能.

make_config(instance_relative=False)

Used to create the config attribute by the Flask constructor. The instance_relative parameter is passed in from the constructor of Flask (there named instance_relative_config) and indicates if the config should be relative to the instance path or the root path of the application.

0.8 新版功能.

make_default_options_response()

This method is called to create the default OPTIONS response. This can be changed through subclassing to change the default behavior of OPTIONS responses.

0.7 新版功能.

make_null_session()

Creates a new instance of a missing session. Instead of overriding this method we recommend replacing the session_interface.

0.7 新版功能.

make_response(rv)

Converts the return value from a view function to a real response object that is an instance of response_class.

The following types are allowed for rv:

response_class	the object is returned unchanged
str	a response object is created with the string as body
unicode	a response object is created with the string encoded to utf-8 as body
a WSGI function	the function is called as WSGI application and buffered as response object
tuple	A tuple in the form (response, status, headers) where response is any of the types defined here, status is a string or an integer and headers is a list of a dictionary with header values.

参数:rv – the return value from the view function

在 0.9 版更改: Previously a tuple was interpreted as the arguments for the response object.

name

The name of the application. This is usually the import name with the difference that it’s guessed from the run file if the import name is main. This name is used as a display name when Flask needs the name of the application. It can be set and overridden to change the value.

0.8 新版功能.

open_instance_resource(resource, mode='rb')

Opens a resource from the application’s instance folder (instance_path). Otherwise works like open_resource(). Instance resources can also be opened for writing.

参数:

• resource – the name of the resource. To access resources within subfolders use forward slashes as separator.
• mode – resource file opening mode, default is ‘rb’.

open_resource(resource, mode='rb')

Opens a resource from the application’s resource folder. To see how this works, consider the following folder structure:

/myapplication.py
/schema.sql
/static
    /style.css
/templates
    /layout.html
    /index.html

If you want to open the schema.sql file you would do the following:

with app.open_resource('schema.sql') as f:
    contents = f.read()
    do_something_with(contents)

参数:

• resource – the name of the resource. To access resources within subfolders use forward slashes as separator.
• mode – resource file opening mode, default is ‘rb’.

open_session(request)

Creates or opens a new session. Default implementation stores all session data in a signed cookie. This requires that the secret_key is set. Instead of overriding this method we recommend replacing the session_interface.

参数:request – an instance of request_class.

permanent_session_lifetime

A timedelta which is used to set the expiration date of a permanent session. The default is 31 days which makes a permanent session survive for roughly one month.

This attribute can also be configured from the config with the PERMANENT_SESSION_LIFETIME configuration key. Defaults to timedelta(days=31)

preprocess_request()

Called before the actual request dispatching and will call every as before_request() decorated function. If any of these function returns a value it’s handled as if it was the return value from the view and further request handling is stopped.

This also triggers the url_value_processor() functions before the actual before_request() functions are called.

preserve_context_on_exception

Returns the value of the PRESERVE_CONTEXT_ON_EXCEPTION configuration value in case it’s set, otherwise a sensible default is returned.

0.7 新版功能.

process_response(response)

Can be overridden in order to modify the response object before it’s sent to the WSGI server. By default this will call all the after_request() decorated functions.

在 0.5 版更改: As of Flask 0.5 the functions registered for after request execution are called in reverse order of registration.

参数:response – a response_class object. 返回:a new response object or the same, has to be an instance of response_class.

propagate_exceptions

Returns the value of the PROPAGATE_EXCEPTIONS configuration value in case it’s set, otherwise a sensible default is returned.

0.7 新版功能.

register_blueprint(*args, **kwargs)

Registers a blueprint on the application.

0.7 新版功能.

register_error_handler(code_or_exception, f)

Alternative error attach function to the errorhandler() decorator that is more straightforward to use for non decorator usage.

0.7 新版功能.

register_module(module, **options)

Registers a module with this application. The keyword argument of this function are the same as the ones for the constructor of the Module class and will override the values of the module if provided.

在 0.7 版更改: The module system was deprecated in favor for the blueprint system.

request_class

The class that is used for request objects. See Request for more information.

Request 的别名

request_context(environ)

Creates a RequestContext from the given environment and binds it to the current context. This must be used in combination with the with statement because the request is only bound to the current context for the duration of the with block.

Example usage:

with app.request_context(environ):
    do_something_with(request)

The object returned can also be used without the with statement which is useful for working in the shell. The example above is doing exactly the same as this code:

ctx = app.request_context(environ)
ctx.push()
try:
    do_something_with(request)
finally:
    ctx.pop()

在 0.3 版更改: Added support for non-with statement usage and with statement is now passed the ctx object.

参数:environ – a WSGI environment

response_class

The class that is used for response objects. See Response for more information.

Response 的别名

route(rule, **options)

A decorator that is used to register a view function for a given URL rule. This does the same thing as add_url_rule() but is intended for decorator usage:

@app.route('/')
def index():
    return 'Hello World'

For more information refer to URL 路由注册.

参数:

• rule – the URL rule as string
• endpoint – the endpoint for the registered URL rule. Flask itself assumes the name of the view function as endpoint
• options – the options to be forwarded to the underlying Rule object. A change to Werkzeug is handling of method options. methods is a list of methods this rule should be limited to (GET, POST etc.). By default a rule just listens for GET (and implicitly HEAD). Starting with Flask 0.6, OPTIONS is implicitly added and handled by the standard request handling.

run(host=None, port=None, debug=None, **options)

Runs the application on a local development server. If the debug flag is set the server will automatically reload for code changes and show a debugger in case an exception happened.

If you want to run the application in debug mode, but disable the code execution on the interactive debugger, you can pass use_evalex=False as parameter. This will keep the debugger’s traceback screen active, but disable code execution.

Keep in Mind

Flask will suppress any server error with a generic error page unless it is in debug mode. As such to enable just the interactive debugger without the code reloading, you have to invoke run() with debug=True and use_reloader=False. Setting use_debugger to True without being in debug mode won’t catch any exceptions because there won’t be any to catch.

在 0.10 版更改: The default port is now picked from the SERVER_NAME variable.

参数:

• host – the hostname to listen on. Set this to '0.0.0.0' to have the server available externally as well. Defaults to '127.0.0.1'.
• port – the port of the webserver. Defaults to 5000 or the port defined in the SERVER_NAME config variable if present.
• debug – if given, enable or disable debug mode. See debug.
• options – the options to be forwarded to the underlying Werkzeug server. See werkzeug.serving.run_simple() for more information.

save_session(session, response)

Saves the session if it needs updates. For the default implementation, check open_session(). Instead of overriding this method we recommend replacing the session_interface.

参数:

• session – the session to be saved (a SecureCookie object)
• response – an instance of response_class

secret_key

If a secret key is set, cryptographic components can use this to sign cookies and other things. Set this to a complex random value when you want to use the secure cookie for instance.

This attribute can also be configured from the config with the SECRET_KEY configuration key. Defaults to None.

select_jinja_autoescape(filename)

Returns True if autoescaping should be active for the given template name.

0.5 新版功能.

send_static_file(filename)

Function used internally to send static files from the static folder to the browser.

0.5 新版功能.

session_cookie_name

The secure cookie uses this for the name of the session cookie.

This attribute can also be configured from the config with the SESSION_COOKIE_NAME configuration key. Defaults to 'session'

session_interface = <flask.sessions.SecureCookieSessionInterface object at 0x2b6bdaab4950>

the session interface to use. By default an instance of SecureCookieSessionInterface is used here.

0.8 新版功能.

should_ignore_error(error)

This is called to figure out if an error should be ignored or not as far as the teardown system is concerned. If this function returns True then the teardown handlers will not be passed the error.

0.10 新版功能.

teardown_appcontext(*args, **kwargs)

Registers a function to be called when the application context ends. These functions are typically also called when the request context is popped.

Example:

ctx = app.app_context()
ctx.push()
...
ctx.pop()

When ctx.pop() is executed in the above example, the teardown functions are called just before the app context moves from the stack of active contexts. This becomes relevant if you are using such constructs in tests.

Since a request context typically also manages an application context it would also be called when you pop a request context.

When a teardown function was called because of an exception it will be passed an error object.

0.9 新版功能.

teardown_appcontext_funcs = None

A list of functions that are called when the application context is destroyed. Since the application context is also torn down if the request ends this is the place to store code that disconnects from databases.

0.9 新版功能.

teardown_request(*args, **kwargs)

Register a function to be run at the end of each request, regardless of whether there was an exception or not. These functions are executed when the request context is popped, even if not an actual request was performed.

Example:

ctx = app.test_request_context()
ctx.push()
...
ctx.pop()

When ctx.pop() is executed in the above example, the teardown functions are called just before the request context moves from the stack of active contexts. This becomes relevant if you are using such constructs in tests.

Generally teardown functions must take every necessary step to avoid that they will fail. If they do execute code that might fail they will have to surround the execution of these code by try/except statements and log occurring errors.

When a teardown function was called because of a exception it will be passed an error object.

Debug Note

In debug mode Flask will not tear down a request on an exception immediately. Instead if will keep it alive so that the interactive debugger can still access it. This behavior can be controlled by the PRESERVE_CONTEXT_ON_EXCEPTION configuration variable.

teardown_request_funcs = None

A dictionary with lists of functions that are called after each request, even if an exception has occurred. The key of the dictionary is the name of the blueprint this function is active for, None for all requests. These functions are not allowed to modify the request, and their return values are ignored. If an exception occurred while processing the request, it gets passed to each teardown_request function. To register a function here, use the teardown_request() decorator.

0.7 新版功能.

template_context_processors = None

A dictionary with list of functions that are called without argument to populate the template context. The key of the dictionary is the name of the blueprint this function is active for, None for all requests. Each returns a dictionary that the template context is updated with. To register a function here, use the context_processor() decorator.

template_filter(*args, **kwargs)

A decorator that is used to register custom template filter. You can specify a name for the filter, otherwise the function name will be used. Example:

@app.template_filter()
def reverse(s):
    return s[::-1]

参数:name – the optional name of the filter, otherwise the function name will be used.

template_global(*args, **kwargs)

A decorator that is used to register a custom template global function. You can specify a name for the global function, otherwise the function name will be used. Example:

@app.template_global()
def double(n):
    return 2 * n

0.10 新版功能.

参数:name – the optional name of the global function, otherwise the function name will be used.

template_test(*args, **kwargs)

A decorator that is used to register custom template test. You can specify a name for the test, otherwise the function name will be used. Example:

@app.template_test()
def is_prime(n):
    if n == 2:
        return True
    for i in range(2, int(math.ceil(math.sqrt(n))) + 1):
        if n % i == 0:
            return False
    return True

0.10 新版功能.

参数:name – the optional name of the test, otherwise the function name will be used.

test_client(use_cookies=True)

Creates a test client for this application. For information about unit testing head over to 测试 Flask 应用.

Note that if you are testing for assertions or exceptions in your application code, you must set app.testing = True in order for the exceptions to propagate to the test client. Otherwise, the exception will be handled by the application (not visible to the test client) and the only indication of an AssertionError or other exception will be a 500 status code response to the test client. See the testing attribute. For example:

app.testing = True
client = app.test_client()

The test client can be used in a with block to defer the closing down of the context until the end of the with block. This is useful if you want to access the context locals for testing:

with app.test_client() as c:
    rv = c.get('/?vodka=42')
    assert request.args['vodka'] == '42'

See FlaskClient for more information.

在 0.4 版更改: added support for with block usage for the client.

0.7 新版功能: The use_cookies parameter was added as well as the ability to override the client to be used by setting the test_client_class attribute.

test_client_class = None

the test client that is used with when test_client is used.

0.7 新版功能.

test_request_context(*args, **kwargs)

Creates a WSGI environment from the given values (see werkzeug.test.EnvironBuilder() for more information, this function accepts the same arguments).

testing

The testing flag. Set this to True to enable the test mode of Flask extensions (and in the future probably also Flask itself). For example this might activate unittest helpers that have an additional runtime cost which should not be enabled by default.

If this is enabled and PROPAGATE_EXCEPTIONS is not changed from the default it’s implicitly enabled.

This attribute can also be configured from the config with the TESTING configuration key. Defaults to False.

trap_http_exception(e)

Checks if an HTTP exception should be trapped or not. By default this will return False for all exceptions except for a bad request key error if TRAP_BAD_REQUEST_ERRORS is set to True. It also returns True if TRAP_HTTP_EXCEPTIONS is set to True.

This is called for all HTTP exceptions raised by a view function. If it returns True for any exception the error handler for this exception is not called and it shows up as regular exception in the traceback. This is helpful for debugging implicitly raised HTTP exceptions.

0.8 新版功能.

update_template_context(context)

Update the template context with some commonly used variables. This injects request, session, config and g into the template context as well as everything template context processors want to inject. Note that the as of Flask 0.6, the original values in the context will not be overridden if a context processor decides to return a value with the same key.

参数:context – the context as a dictionary that is updated in place to add extra variables.

url_build_error_handlers = None

A list of functions that are called when url_for() raises a BuildError. Each function registered here is called with error, endpoint and values. If a function returns None or raises a BuildError the next function is tried.

0.9 新版功能.

url_default_functions = None

A dictionary with lists of functions that can be used as URL value preprocessors. The key None here is used for application wide callbacks, otherwise the key is the name of the blueprint. Each of these functions has the chance to modify the dictionary of URL values before they are used as the keyword arguments of the view function. For each function registered this one should also provide a url_defaults() function that adds the parameters automatically again that were removed that way.

0.7 新版功能.

url_defaults(*args, **kwargs)

Callback function for URL defaults for all view functions of the application. It’s called with the endpoint and values and should update the values passed in place.

url_map = None

The Map for this instance. You can use this to change the routing converters after the class was created but before any routes are connected. Example:

from werkzeug.routing import BaseConverter

class ListConverter(BaseConverter):
    def to_python(self, value):
        return value.split(',')
    def to_url(self, values):
        return ','.join(BaseConverter.to_url(value)
                        for value in values)

app = Flask(__name__)
app.url_map.converters['list'] = ListConverter

url_rule_class

The rule object to use for URL rules created. This is used by add_url_rule(). Defaults to werkzeug.routing.Rule.

0.7 新版功能.

Rule 的别名

url_value_preprocessor(*args, **kwargs)

Registers a function as URL value preprocessor for all view functions of the application. It’s called before the view functions are called and can modify the url values provided.

url_value_preprocessors = None

A dictionary with lists of functions that can be used as URL value processor functions. Whenever a URL is built these functions are called to modify the dictionary of values in place. The key None here is used for application wide callbacks, otherwise the key is the name of the blueprint. Each of these functions has the chance to modify the dictionary

0.7 新版功能.

use_x_sendfile

Enable this if you want to use the X-Sendfile feature. Keep in mind that the server has to support this. This only affects files sent with the send_file() method.

0.2 新版功能.

This attribute can also be configured from the config with the USE_X_SENDFILE configuration key. Defaults to False.

view_functions = None

A dictionary of all view functions registered. The keys will be function names which are also used to generate URLs and the values are the function objects themselves. To register a view function, use the route() decorator.

wsgi_app(environ, start_response)

The actual WSGI application. This is not implemented in __call__ so that middlewares can be applied without losing a reference to the class. So instead of doing this:

app = MyMiddleware(app)

It’s a better idea to do this instead:

app.wsgi_app = MyMiddleware(app.wsgi_app)

Then you still have the original application object around and can continue to call methods on it.

在 0.7 版更改: The behavior of the before and after request callbacks was changed under error conditions and a new callback was added that will always execute at the end of the request, independent on if an error occurred or not. See 回调和错误.

参数:

• environ – a WSGI environment
• start_response – a callable accepting a status code, a list of headers and an optional exception context to start the response

蓝图对象

class flask.Blueprint(name, import_name, static_folder=None, static_url_path=None, template_folder=None, url_prefix=None, subdomain=None, url_defaults=None)

Represents a blueprint. A blueprint is an object that records functions that will be called with the BlueprintSetupState later to register functions or other things on the main application. See 用蓝图实现模块化的应用 for more information.

0.7 新版功能.

add_app_template_filter(f, name=None)

Register a custom template filter, available application wide. Like Flask.add_template_filter() but for a blueprint. Works exactly like the app_template_filter() decorator.

参数:name – the optional name of the filter, otherwise the function name will be used.

add_app_template_global(f, name=None)

Register a custom template global, available application wide. Like Flask.add_template_global() but for a blueprint. Works exactly like the app_template_global() decorator.

0.10 新版功能.

参数:name – the optional name of the global, otherwise the function name will be used.

add_app_template_test(f, name=None)

Register a custom template test, available application wide. Like Flask.add_template_test() but for a blueprint. Works exactly like the app_template_test() decorator.

0.10 新版功能.

参数:name – the optional name of the test, otherwise the function name will be used.

add_url_rule(rule, endpoint=None, view_func=None, **options)

Like Flask.add_url_rule() but for a blueprint. The endpoint for the url_for() function is prefixed with the name of the blueprint.

after_app_request(f)

Like Flask.after_request() but for a blueprint. Such a function is executed after each request, even if outside of the blueprint.

after_request(f)

Like Flask.after_request() but for a blueprint. This function is only executed after each request that is handled by a function of that blueprint.

app_context_processor(f)

Like Flask.context_processor() but for a blueprint. Such a function is executed each request, even if outside of the blueprint.

app_errorhandler(code)

Like Flask.errorhandler() but for a blueprint. This handler is used for all requests, even if outside of the blueprint.

app_template_filter(name=None)

Register a custom template filter, available application wide. Like Flask.template_filter() but for a blueprint.

参数:name – the optional name of the filter, otherwise the function name will be used.

app_template_global(name=None)

Register a custom template global, available application wide. Like Flask.template_global() but for a blueprint.

0.10 新版功能.

参数:name – the optional name of the global, otherwise the function name will be used.

app_template_test(name=None)

Register a custom template test, available application wide. Like Flask.template_test() but for a blueprint.

0.10 新版功能.

参数:name – the optional name of the test, otherwise the function name will be used.

app_url_defaults(f)

Same as url_defaults() but application wide.

app_url_value_preprocessor(f)

Same as url_value_preprocessor() but application wide.

before_app_first_request(f)

Like Flask.before_first_request(). Such a function is executed before the first request to the application.

before_app_request(f)

Like Flask.before_request(). Such a function is executed before each request, even if outside of a blueprint.

before_request(f)

Like Flask.before_request() but for a blueprint. This function is only executed before each request that is handled by a function of that blueprint.

context_processor(f)

Like Flask.context_processor() but for a blueprint. This function is only executed for requests handled by a blueprint.

endpoint(endpoint)

Like Flask.endpoint() but for a blueprint. This does not prefix the endpoint with the blueprint name, this has to be done explicitly by the user of this method. If the endpoint is prefixed with a . it will be registered to the current blueprint, otherwise it’s an application independent endpoint.

errorhandler(code_or_exception)

Registers an error handler that becomes active for this blueprint only. Please be aware that routing does not happen local to a blueprint so an error handler for 404 usually is not handled by a blueprint unless it is caused inside a view function. Another special case is the 500 internal server error which is always looked up from the application.

Otherwise works as the errorhandler() decorator of the Flask object.

get_send_file_max_age(filename)

Provides default cache_timeout for the send_file() functions.

By default, this function returns SEND_FILE_MAX_AGE_DEFAULT from the configuration of current_app.

Static file functions such as send_from_directory() use this function, and send_file() calls this function on current_app when the given cache_timeout is None. If a cache_timeout is given in send_file(), that timeout is used; otherwise, this method is called.

This allows subclasses to change the behavior when sending files based on the filename. For example, to set the cache timeout for .js files to 60 seconds:

class MyFlask(flask.Flask):
    def get_send_file_max_age(self, name):
        if name.lower().endswith('.js'):
            return 60
        return flask.Flask.get_send_file_max_age(self, name)

0.9 新版功能.

has_static_folder

This is True if the package bound object’s container has a folder named 'static'.

0.5 新版功能.

jinja_loader

The Jinja loader for this package bound object.

0.5 新版功能.

make_setup_state(app, options, first_registration=False)

Creates an instance of BlueprintSetupState() object that is later passed to the register callback functions. Subclasses can override this to return a subclass of the setup state.

open_resource(resource, mode='rb')

Opens a resource from the application’s resource folder. To see how this works, consider the following folder structure:

/myapplication.py
/schema.sql
/static
    /style.css
/templates
    /layout.html
    /index.html

If you want to open the schema.sql file you would do the following:

with app.open_resource('schema.sql') as f:
    contents = f.read()
    do_something_with(contents)

参数:

• resource – the name of the resource. To access resources within subfolders use forward slashes as separator.
• mode – resource file opening mode, default is ‘rb’.

record(func)

Registers a function that is called when the blueprint is registered on the application. This function is called with the state as argument as returned by the make_setup_state() method.

record_once(func)

Works like record() but wraps the function in another function that will ensure the function is only called once. If the blueprint is registered a second time on the application, the function passed is not called.

register(app, options, first_registration=False)

Called by Flask.register_blueprint() to register a blueprint on the application. This can be overridden to customize the register behavior. Keyword arguments from register_blueprint() are directly forwarded to this method in the options dictionary.

route(rule, **options)

Like Flask.route() but for a blueprint. The endpoint for the url_for() function is prefixed with the name of the blueprint.

send_static_file(filename)

Function used internally to send static files from the static folder to the browser.

0.5 新版功能.

teardown_app_request(f)

Like Flask.teardown_request() but for a blueprint. Such a function is executed when tearing down each request, even if outside of the blueprint.

teardown_request(f)

Like Flask.teardown_request() but for a blueprint. This function is only executed when tearing down requests handled by a function of that blueprint. Teardown request functions are executed when the request context is popped, even when no actual request was performed.

url_defaults(f)

Callback function for URL defaults for this blueprint. It’s called with the endpoint and values and should update the values passed in place.

url_value_preprocessor(f)

Registers a function as URL value preprocessor for this blueprint. It’s called before the view functions are called and can modify the url values provided.

进入的请求对象

class flask.Request(environ, populate_request=True, shallow=False)

The request object used by default in Flask. Remembers the matched endpoint and view arguments.

It is what ends up as request. If you want to replace the request object used you can subclass this and set request_class to your subclass.

The request object is a Request subclass and provides all of the attributes Werkzeug defines plus a few Flask specific ones.

form

一个包含解析过的从 POST 或 PUT 请求发送的表单对象的 MultiDict 。请注意上传的文件不会在这里，而是在 files 属性中。

args

一个包含解析过的查询字符串（ URL 中问号后的部分）内容的 MultiDict 。

values

一个包含 form 和 args 全部内容的 CombinedMultiDict 。

cookies

一个包含请求中传送的所有 cookie 内容的 dict 。

stream

如果表单提交的数据没有以已知的 mimetype 编码，为性能考虑，数据会不经 修改存储在这个流中。大多数情况下，使用可以把数据提供为字符串的 data 是更好的方法。流只返回一次数据。

headers

进入请求的标头存为一个类似字典的对象。

data

如果进入的请求数据是 Flask 不能处理的 mimetype ，数据将作为字符串 存于此。

files

一个包含 POST 和 PUT 请求中上传的文件的 MultiDict 。每个文件存储为 FileStorage 对象。其基本的行为类似你在 Python 中 见到的标准文件对象，差异在于这个对象有一个 save() 方法可以把文件存储到文件系统上。

environ

底层的 WSGI 环境。

method

当前请求的 HTTP 方法 (POST ， GET 等等)

path

script_root

url

base_url

url_root

提供不同的方式来审视当前的 URL 。想象你的应用监听下面的 URL:

http://www.example.com/myapplication

并且用户请求下面的 URL:

http://www.example.com/myapplication/page.html?x=y

这个情况下，上面提到的属性的值会为如下:

path	/page.html
script_root	/myapplication
base_url	http://www.example.com/myapplication/page.html
url	http://www.example.com/myapplication/page.html?x=y
url_root	http://www.example.com/myapplication/

is_xhr

当请求由 JavaScript 的 XMLHttpRequest 触发时，该值为 True 。 这只对支持 X-Requested-With 标头并把该标头设置为 XMLHttpRequest 的库奏效。这么做的库有 prototype 、 jQuery 以及 Mochikit 等更多。

blueprint

The name of the current blueprint

endpoint

The endpoint that matched the request. This in combination with view_args can be used to reconstruct the same or a modified URL. If an exception happened when matching, this will be None.

get_json(force=False, silent=False, cache=True)

Parses the incoming JSON request data and returns it. If parsing fails the on_json_loading_failed() method on the request object will be invoked. By default this function will only load the json data if the mimetype is application/json but this can be overriden by the force parameter.

参数:

• force – if set to True the mimetype is ignored.
• silent – if set to False this method will fail silently and return False.
• cache – if set to True the parsed JSON data is remembered on the request.

json

If the mimetype is application/json this will contain the parsed JSON data. Otherwise this will be None.

The get_json() method should be used instead.

max_content_length

Read-only view of the MAX_CONTENT_LENGTH config key.

module

The name of the current module if the request was dispatched to an actual module. This is deprecated functionality, use blueprints instead.

on_json_loading_failed(e)

Called if decoding of the JSON data failed. The return value of this method is used by get_json() when an error occurred. The default implementation just raises a BadRequest exception.

在 0.10 版更改: Removed buggy previous behavior of generating a random JSON response. If you want that behavior back you can trivially add it by subclassing.

0.8 新版功能.

routing_exception = None

if matching the URL failed, this is the exception that will be raised / was raised as part of the request handling. This is usually a NotFound exception or something similar.

url_rule = None

the internal URL rule that matched the request. This can be useful to inspect which methods are allowed for the URL from a before/after handler (request.url_rule.methods) etc.

0.6 新版功能.

view_args = None

a dict of view arguments that matched the request. If an exception happened when matching, this will be None.

class flask.request

你可以使用全局 request 对象访问进入的请求数据。 Flask 处理进入的请求 数据并允许你用这个全局对象访问它。如果你工作在多线程环境，Flask 内部保证 你总会在当前线程上获取正确的数据，

这是一个代理。详情见 留意代理 。

请求对象是一个 Request 子类的实例，提供所有 Werkzeug 定义的属性。这里只对最重要的展示了简要概述。

响应对象

class flask.Response(response=None, status=None, headers=None, mimetype=None, content_type=None, direct_passthrough=False)

The response object that is used by default in Flask. Works like the response object from Werkzeug but is set to have an HTML mimetype by default. Quite often you don’t have to create this object yourself because make_response() will take care of that for you.

If you want to replace the response object used you can subclass this and set response_class to your subclass.

headers

Headers 对象表示响应的标头。

status

字符串表示的响应状态。

status_code

整数表示的响应状态。

data

A descriptor that calls get_data() and set_data(). This should not be used and will eventually get deprecated.

mimetype

The mimetype (content type without charset etc.)

set_cookie(key, value='', max_age=None, expires=None, path='/', domain=None, secure=None, httponly=False)

Sets a cookie. The parameters are the same as in the cookie Morsel object in the Python standard library but it accepts unicode data, too.

参数:

• key – the key (name) of the cookie to be set.
• value – the value of the cookie.
• max_age – should be a number of seconds, or None (default) if the cookie should last only as long as the client’s browser session.
• expires – should be a datetime object or UNIX timestamp.
• domain – if you want to set a cross-domain cookie. For example, domain=".example.com" will set a cookie that is readable by the domain www.example.com, foo.example.com etc. Otherwise, a cookie will only be readable by the domain that set it.
• path – limits the cookie to a given path, per default it will span the whole domain.

会话

如果你设置了 Flask.secret_key ，你可以在 Flask 应用中使用会话。会话 主要使得在请求见保留信息成为可能。 Flask 的实现方法是使用一个签名的 cookie 。 这样，用户可以查看会话的内容，但是不能修改它，除非用户知道密钥。所以确保密钥 被设置为一个复杂且无法被容易猜测的值。

你可以使用 session 对象来访问当前的会话:

class flask.session

会话对象很像通常的字典，区别是会话对象会追踪修改。

这是一个代理。更多信息见 留意代理 。

下列属性是需要关注的:

new

如果会话是新的，该值为 True ，否则为 False 。

modified

当果会话对象检测到修改，这个值为 True 。注意可变结构的修改不会 被自动捕获，这种情况下你需要自行显式地设置这个属性为 True 。这 里有 一个例子:

# this change is not picked up because a mutable object (here
# a list) is changed.
session['objects'].append(42)
# so mark it as modified yourself
session.modified = True

permanent

如果设为 True ，会话存活 permanent_session_lifetime 秒。默认为 31 天。 如果是 False （默认选项），会话会在用户关闭浏览器时删除。

会话接口

0.8 新版功能.

会话接口提供了简单的途径来替换 Flask 正在使用的会话实现。

class flask.sessions.SessionInterface

The basic interface you have to implement in order to replace the default session interface which uses werkzeug’s securecookie implementation. The only methods you have to implement are open_session() and save_session(), the others have useful defaults which you don’t need to change.

The session object returned by the open_session() method has to provide a dictionary like interface plus the properties and methods from the SessionMixin. We recommend just subclassing a dict and adding that mixin:

class Session(dict, SessionMixin):
    pass

If open_session() returns None Flask will call into make_null_session() to create a session that acts as replacement if the session support cannot work because some requirement is not fulfilled. The default NullSession class that is created will complain that the secret key was not set.

To replace the session interface on an application all you have to do is to assign flask.Flask.session_interface:

app = Flask(__name__)
app.session_interface = MySessionInterface()

0.8 新版功能.

get_cookie_domain(app)

Helpful helper method that returns the cookie domain that should be used for the session cookie if session cookies are used.

get_cookie_httponly(app)

Returns True if the session cookie should be httponly. This currently just returns the value of the SESSION_COOKIE_HTTPONLY config var.

get_cookie_path(app)

Returns the path for which the cookie should be valid. The default implementation uses the value from the SESSION_COOKIE_PATH`` config var if it’s set, and falls back to APPLICATION_ROOT or uses / if it’s None.

get_cookie_secure(app)

Returns True if the cookie should be secure. This currently just returns the value of the SESSION_COOKIE_SECURE setting.

get_expiration_time(app, session)

A helper method that returns an expiration date for the session or None if the session is linked to the browser session. The default implementation returns now + the permanent session lifetime configured on the application.

is_null_session(obj)

Checks if a given object is a null session. Null sessions are not asked to be saved.

This checks if the object is an instance of null_session_class by default.

make_null_session(app)

Creates a null session which acts as a replacement object if the real session support could not be loaded due to a configuration error. This mainly aids the user experience because the job of the null session is to still support lookup without complaining but modifications are answered with a helpful error message of what failed.

This creates an instance of null_session_class by default.

null_session_class

make_null_session() will look here for the class that should be created when a null session is requested. Likewise the is_null_session() method will perform a typecheck against this type.

NullSession 的别名

open_session(app, request)

This method has to be implemented and must either return None in case the loading failed because of a configuration error or an instance of a session object which implements a dictionary like interface + the methods and attributes on SessionMixin.

pickle_based = False

A flag that indicates if the session interface is pickle based. This can be used by flask extensions to make a decision in regards to how to deal with the session object.

0.10 新版功能.

save_session(app, session, response)

This is called for actual sessions returned by open_session() at the end of the request. This is still called during a request context so if you absolutely need access to the request you can do that.

class flask.sessions.SecureCookieSessionInterface

The default session interface that stores sessions in signed cookies through the itsdangerous module.

digest_method()

the hash function to use for the signature. The default is sha1

key_derivation = 'hmac'

the name of the itsdangerous supported key derivation. The default is hmac.

salt = 'cookie-session'

the salt that should be applied on top of the secret key for the signing of cookie based sessions.

serializer = <flask.sessions.TaggedJSONSerializer object at 0x2b6bdaab4510>

A python serializer for the payload. The default is a compact JSON derived serializer with support for some extra Python types such as datetime objects or tuples.

session_class

SecureCookieSession 的别名

class flask.sessions.NullSession(initial=None)

Class used to generate nicer error messages if sessions are not available. Will still allow read-only access to the empty session but fail on setting.

class flask.sessions.SessionMixin

Expands a basic dictionary with an accessors that are expected by Flask extensions and users for the session.

modified = True

for some backends this will always be True, but some backends will default this to false and detect changes in the dictionary for as long as changes do not happen on mutable structures in the session. The default mixin implementation just hardcodes True in.

new = False

some session backends can tell you if a session is new, but that is not necessarily guaranteed. Use with caution. The default mixin implementation just hardcodes False in.

permanent

this reflects the '_permanent' key in the dict.

flask.sessions.session_json_serializer

Notice

PERMANENT_SESSION_LIFETIME 配置键从 Flask 0.8 开始可以是一个整数。 你可以自己计算值，或用应用上的 permanent_session_lifetime 属性来自动转换结果为 一个整数。

测试客户端

class flask.testing.FlaskClient(application, response_wrapper=None, use_cookies=True, allow_subdomain_redirects=False)

Works like a regular Werkzeug test client but has some knowledge about how Flask works to defer the cleanup of the request context stack to the end of a with body when used in a with statement. For general information about how to use this class refer to werkzeug.test.Client.

Basic usage is outlined in the 测试 Flask 应用 chapter.

session_transaction(*args, **kwds)

When used in combination with a with statement this opens a session transaction. This can be used to modify the session that the test client uses. Once the with block is left the session is stored back.

with client.session_transaction() as session:

session[‘value’] = 42

Internally this is implemented by going through a temporary test request context and since session handling could depend on request variables this function accepts the same arguments as test_request_context() which are directly passed through.

应用全局变量

只在一个请求内，从一个函数到另一个函数共享数据，全局变量并不够好。因为这 在线程环境下行不通。 Flask 提供了一个特殊的对象来确保只在活动的请求中 有效，并且每个请求都返回不同的值。一言蔽之：它做正确的事情，如同它对 request 和 session 做的那样。

flask.g

在这上存储你任何你想要存储的。例如一个数据库连接或者当前登入的用户。

从 Flask 0.10 起，对象 g 存储在应用上下文中而不再是请求上下文中，这 意味着即使在应用上下文中它也是可访问的而不是只能在请求上下文中。在 结合 伪造资源和上下文 模式使用来测试时这尤为有用。

另外，在 0.10 中你可以使用 get() 方法来获取一个属性或者如果这 个属性没设置的话将得到 None (或者第二个参数)。 这两种用法现在是没有区别的:

user = getattr(flask.g, 'user', None)
user = flask.get.get('user', None)

现在也能在 g 对象上使用 in 运算符来确定它是否有某个属性，并且它 将使用 yield 关键字来生成这样一个可迭代的包含所有keys的生成器。

这是一个代理。详情见 留意代理 。

有用的函数和类

flask.current_app

指向正在处理请求的应用。这对于想要支持同时运行多个应用的扩展有用。 它由应用上下文驱动，而不是请求上下文，所以你可以用 app_context() 方法 修改这个代理的值。

这是一个代理。详情见 留意代理 。

flask.has_request_context()

If you have code that wants to test if a request context is there or not this function can be used. For instance, you may want to take advantage of request information if the request object is available, but fail silently if it is unavailable.

class User(db.Model):

    def __init__(self, username, remote_addr=None):
        self.username = username
        if remote_addr is None and has_request_context():
            remote_addr = request.remote_addr
        self.remote_addr = remote_addr

Alternatively you can also just test any of the context bound objects (such as request or g for truthness):

class User(db.Model):

    def __init__(self, username, remote_addr=None):
        self.username = username
        if remote_addr is None and request:
            remote_addr = request.remote_addr
        self.remote_addr = remote_addr

0.7 新版功能.

flask.has_app_context()

Works like has_request_context() but for the application context. You can also just do a boolean check on the current_app object instead.

0.9 新版功能.

flask.url_for(endpoint, **values)

Generates a URL to the given endpoint with the method provided.

Variable arguments that are unknown to the target endpoint are appended to the generated URL as query arguments. If the value of a query argument is None, the whole pair is skipped. In case blueprints are active you can shortcut references to the same blueprint by prefixing the local endpoint with a dot (.).

This will reference the index function local to the current blueprint:

url_for('.index')

For more information, head over to the Quickstart.

To integrate applications, Flask has a hook to intercept URL build errors through Flask.build_error_handler. The url_for function results in a BuildError when the current app does not have a URL for the given endpoint and values. When it does, the current_app calls its build_error_handler if it is not None, which can return a string to use as the result of url_for (instead of url_for‘s default to raise the BuildError exception) or re-raise the exception. An example:

def external_url_handler(error, endpoint, **values):
    "Looks up an external URL when `url_for` cannot build a URL."
    # This is an example of hooking the build_error_handler.
    # Here, lookup_url is some utility function you've built
    # which looks up the endpoint in some external URL registry.
    url = lookup_url(endpoint, **values)
    if url is None:
        # External lookup did not have a URL.
        # Re-raise the BuildError, in context of original traceback.
        exc_type, exc_value, tb = sys.exc_info()
        if exc_value is error:
            raise exc_type, exc_value, tb
        else:
            raise error
    # url_for will use this result, instead of raising BuildError.
    return url

app.build_error_handler = external_url_handler

Here, error is the instance of BuildError, and endpoint and **values are the arguments passed into url_for. Note that this is for building URLs outside the current application, and not for handling 404 NotFound errors.

0.10 新版功能: The _scheme parameter was added.

0.9 新版功能: The _anchor and _method parameters were added.

0.9 新版功能: Calls Flask.handle_build_error() on BuildError.

参数:

• endpoint – the endpoint of the URL (name of the function)
• values – the variable arguments of the URL rule
• _external – if set to True, an absolute URL is generated. Server address can be changed via SERVER_NAME configuration variable which defaults to localhost.
• _scheme – a string specifying the desired URL scheme. The _external parameter must be set to True or a ValueError is raised.
• _anchor – if provided this is added as anchor to the URL.
• _method – if provided this explicitly specifies an HTTP method.

flask.abort(code)

抛出一个给定状态代码的 HTTPException 。 例如想要用一个页面未找到异常来终止请求，你可以调用 abort(404) 。

参数:code – the HTTP error code.

flask.redirect(location, code=302)

Return a response object (a WSGI application) that, if called, redirects the client to the target location. Supported codes are 301, 302, 303, 305, and 307. 300 is not supported because it’s not a real redirect and 304 because it’s the answer for a request with a request with defined If-Modified-Since headers.

0.6 新版功能: The location can now be a unicode string that is encoded using the iri_to_uri() function.

参数:

• location – the location the response should redirect to.
• code – the redirect status code. defaults to 302.

flask.make_response(*args)

Sometimes it is necessary to set additional headers in a view. Because views do not have to return response objects but can return a value that is converted into a response object by Flask itself, it becomes tricky to add headers to it. This function can be called instead of using a return and you will get a response object which you can use to attach headers.

If view looked like this and you want to add a new header:

def index():
    return render_template('index.html', foo=42)

You can now do something like this:

def index():
    response = make_response(render_template('index.html', foo=42))
    response.headers['X-Parachutes'] = 'parachutes are cool'
    return response

This function accepts the very same arguments you can return from a view function. This for example creates a response with a 404 error code:

response = make_response(render_template('not_found.html'), 404)

The other use case of this function is to force the return value of a view function into a response which is helpful with view decorators:

response = make_response(view_function())
response.headers['X-Parachutes'] = 'parachutes are cool'

Internally this function does the following things:

• if no arguments are passed, it creates a new response argument
• if one argument is passed, flask.Flask.make_response() is invoked with it.
• if more than one argument is passed, the arguments are passed to the flask.Flask.make_response() function as tuple.

0.6 新版功能.

flask.send_file(filename_or_fp, mimetype=None, as_attachment=False, attachment_filename=None, add_etags=True, cache_timeout=None, conditional=False)

Sends the contents of a file to the client. This will use the most efficient method available and configured. By default it will try to use the WSGI server’s file_wrapper support. Alternatively you can set the application’s use_x_sendfile attribute to True to directly emit an X-Sendfile header. This however requires support of the underlying webserver for X-Sendfile.

By default it will try to guess the mimetype for you, but you can also explicitly provide one. For extra security you probably want to send certain files as attachment (HTML for instance). The mimetype guessing requires a filename or an attachment_filename to be provided.

Please never pass filenames to this function from user sources without checking them first. Something like this is usually sufficient to avoid security problems:

if '..' in filename or filename.startswith('/'):
    abort(404)

0.2 新版功能.

0.5 新版功能: The add_etags, cache_timeout and conditional parameters were added. The default behavior is now to attach etags.

在 0.7 版更改: mimetype guessing and etag support for file objects was deprecated because it was unreliable. Pass a filename if you are able to, otherwise attach an etag yourself. This functionality will be removed in Flask 1.0

在 0.9 版更改: cache_timeout pulls its default from application config, when None.

参数:

• filename_or_fp – the filename of the file to send. This is relative to the root_path if a relative path is specified. Alternatively a file object might be provided in which case X-Sendfile might not work and fall back to the traditional method. Make sure that the file pointer is positioned at the start of data to send before calling send_file().
• mimetype – the mimetype of the file if provided, otherwise auto detection happens.
• as_attachment – set to True if you want to send this file with a Content-Disposition: attachment header.
• attachment_filename – the filename for the attachment if it differs from the file’s filename.
• add_etags – set to False to disable attaching of etags.
• conditional – set to True to enable conditional responses.
• cache_timeout – the timeout in seconds for the headers. When None (default), this value is set by get_send_file_max_age() of current_app.

flask.send_from_directory(directory, filename, **options)

Send a file from a given directory with send_file(). This is a secure way to quickly expose static files from an upload folder or something similar.

Example usage:

@app.route('/uploads/<path:filename>')
def download_file(filename):
    return send_from_directory(app.config['UPLOAD_FOLDER'],
                               filename, as_attachment=True)

Sending files and Performance

It is strongly recommended to activate either X-Sendfile support in your webserver or (if no authentication happens) to tell the webserver to serve files for the given path on its own without calling into the web application for improved performance.

0.5 新版功能.

参数:

• directory – the directory where all the files are stored.
• filename – the filename relative to that directory to download.
• options – optional keyword arguments that are directly forwarded to send_file().

flask.safe_join(directory, filename)

Safely join directory and filename.

Example usage:

@app.route('/wiki/<path:filename>')
def wiki_page(filename):
    filename = safe_join(app.config['WIKI_FOLDER'], filename)
    with open(filename, 'rb') as fd:
        content = fd.read() # Read and process the file content...

参数:

• directory – the base directory.
• filename – the untrusted filename relative to that directory.

Raises:

NotFound if the resulting path would fall out of directory.

flask.escape(s) → markup

Convert the characters &, <, >, ‘, and ” in string s to HTML-safe sequences. Use this if you need to display text that might contain such characters in HTML. Marks return value as markup string.

class flask.Markup

Marks a string as being safe for inclusion in HTML/XML output without needing to be escaped. This implements the __html__ interface a couple of frameworks and web applications use. Markup is a direct subclass of unicode and provides all the methods of unicode just that it escapes arguments passed and always returns Markup.

The escape function returns markup objects so that double escaping can’t happen.

The constructor of the Markup class can be used for three different things: When passed an unicode object it’s assumed to be safe, when passed an object with an HTML representation (has an __html__ method) that representation is used, otherwise the object passed is converted into a unicode string and then assumed to be safe:

>>> Markup("Hello <em>World</em>!")
Markup(u'Hello <em>World</em>!')
>>> class Foo(object):
...  def __html__(self):
...   return '<a href="#">foo</a>'
...
>>> Markup(Foo())
Markup(u'<a href="#">foo</a>')

If you want object passed being always treated as unsafe you can use the escape() classmethod to create a Markup object:

>>> Markup.escape("Hello <em>World</em>!")
Markup(u'Hello &lt;em&gt;World&lt;/em&gt;!')

Operations on a markup string are markup aware which means that all arguments are passed through the escape() function:

>>> em = Markup("<em>%s</em>")
>>> em % "foo & bar"
Markup(u'<em>foo &amp; bar</em>')
>>> strong = Markup("<strong>%(text)s</strong>")
>>> strong % {'text': '<blink>hacker here</blink>'}
Markup(u'<strong>&lt;blink&gt;hacker here&lt;/blink&gt;</strong>')
>>> Markup("<em>Hello</em> ") + "<foo>"
Markup(u'<em>Hello</em> &lt;foo&gt;')

classmethod escape(s)

Escape the string. Works like escape() with the difference that for subclasses of Markup this function would return the correct subclass.

striptags()

Unescape markup into an text_type string and strip all tags. This also resolves known HTML4 and XHTML entities. Whitespace is normalized to one:

>>> Markup("Main &raquo;  <em>About</em>").striptags()
u'Main \xbb About'

unescape()

Unescape markup again into an text_type string. This also resolves known HTML4 and XHTML entities:

>>> Markup("Main &raquo; <em>About</em>").unescape()
u'Main \xbb <em>About</em>'

消息闪现

flask.flash(message, category='message')

Flashes a message to the next request. In order to remove the flashed message from the session and to display it to the user, the template has to call get_flashed_messages().

在 0.3 版更改: category parameter added.

参数:

• message – the message to be flashed.
• category – the category for the message. The following values are recommended: 'message' for any kind of message, 'error' for errors, 'info' for information messages and 'warning' for warnings. However any kind of string can be used as category.

flask.get_flashed_messages(with_categories=False, category_filter=[])

Pulls all flashed messages from the session and returns them. Further calls in the same request to the function will return the same messages. By default just the messages are returned, but when with_categories is set to True, the return value will be a list of tuples in the form (category, message) instead.

Filter the flashed messages to one or more categories by providing those categories in category_filter. This allows rendering categories in separate html blocks. The with_categories and category_filter arguments are distinct:

• with_categories controls whether categories are returned with message text (True gives a tuple, where False gives just the message text).
• category_filter filters the messages down to only those matching the provided categories.

See 消息闪现 for examples.

在 0.3 版更改: with_categories parameter added.

在 0.9 版更改: category_filter parameter added.

参数:

• with_categories – set to True to also receive categories.
• category_filter – whitelist of categories to limit return values

JSON 支持

Flask 使用 simplejson 来实现JSON。自从 simplejson 既在标准库中提供也在 Flask 的拓展中提供。Flask将首先尝试自带的simplejson，如果失败了就使用标准 库中的json模块。除此之外，为了更容易定制它还会委托访问当前应用的JSON的编码 器和解码器。

所以首先不要这样用：

try:

import simplejson as json

except ImportError:

import json

你可以这样

from flask import json

For usage examples, read the json documentation. 关于更多的用法，请阅读标准库中的 json 文档。下面的拓展已经默认被集成 到了标准库中JSON模块里：

1. datetime 对象被序列化为 RFC 822 字符串。
2. 任何带有 __html__ 方法(比如 Markup)将在序列化的时候 调用这个方法然后返回的字符串将会被序列化为字符串。

这个 htmlsafe_dumps() 方法也能在 Jinja2 的过滤器中使用，名字为 |tojson 。请注意在 script 标签内部的内容将不会被转义，所以如果你想在 script 内部使用的话请确保它是不可用的通过 |safe 来转义，除非你正在 使用 Flask 0.10，如下：

<script type=text/javascript>
    doSomethingWith({{ user.username|tojson|safe }});
</script>

flask.json.jsonify(*args, **kwargs)

Creates a Response with the JSON representation of the given arguments with an application/json mimetype. The arguments to this function are the same as to the dict constructor.

Example usage:

from flask import jsonify

@app.route('/_get_current_user')
def get_current_user():
    return jsonify(username=g.user.username,
                   email=g.user.email,
                   id=g.user.id)

This will send a JSON response like this to the browser:

{
    "username": "admin",
    "email": "admin@localhost",
    "id": 42
}

For security reasons only objects are supported toplevel. For more information about this, have a look at JSON 安全.

This function’s response will be pretty printed if it was not requested with X-Requested-With: XMLHttpRequest to simplify debugging unless the JSONIFY_PRETTYPRINT_REGULAR config parameter is set to false.

0.2 新版功能.

flask.json.dumps(obj, **kwargs)

Serialize obj to a JSON formatted str by using the application’s configured encoder (json_encoder) if there is an application on the stack.

This function can return unicode strings or ascii-only bytestrings by default which coerce into unicode strings automatically. That behavior by default is controlled by the JSON_AS_ASCII configuration variable and can be overriden by the simplejson ensure_ascii parameter.

flask.json.dump(obj, fp, **kwargs)

Like dumps() but writes into a file object.

flask.json.loads(s, **kwargs)

Unserialize a JSON object from a string s by using the application’s configured decoder (json_decoder) if there is an application on the stack.

flask.json.load(fp, **kwargs)

Like loads() but reads from a file object.

class flask.json.JSONEncoder(skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, sort_keys=False, indent=None, separators=None, encoding='utf-8', default=None)

The default Flask JSON encoder. This one extends the default simplejson encoder by also supporting datetime objects, UUID as well as Markup objects which are serialized as RFC 822 datetime strings (same as the HTTP date format). In order to support more data types override the default() method.

default(o)

Implement this method in a subclass such that it returns a serializable object for o, or calls the base implementation (to raise a TypeError).

For example, to support arbitrary iterators, you could implement default like this:

def default(self, o):
    try:
        iterable = iter(o)
    except TypeError:
        pass
    else:
        return list(iterable)
    return JSONEncoder.default(self, o)

class flask.json.JSONDecoder(encoding=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, strict=True, object_pairs_hook=None)

The default JSON decoder. This one does not change the behavior from the default simplejson encoder. Consult the json documentation for more information. This decoder is not only used for the load functions of this module but also Request.

模板渲染

flask.render_template(template_name_or_list, **context)

Renders a template from the template folder with the given context.

参数:

• template_name_or_list – the name of the template to be rendered, or an iterable with template names the first one existing will be rendered
• context – the variables that should be available in the context of the template.

flask.render_template_string(source, **context)

Renders a template from the given template source string with the given context.

参数:

• source – the sourcecode of the template to be rendered
• context – the variables that should be available in the context of the template.

flask.get_template_attribute(template_name, attribute)

Loads a macro (or variable) a template exports. This can be used to invoke a macro from within Python code. If you for example have a template named _cider.html with the following contents:

{% macro hello(name) %}Hello {{ name }}!{% endmacro %}

You can access this from Python code like this:

hello = get_template_attribute('_cider.html', 'hello')
return hello('World')

0.2 新版功能.

参数:

• template_name – the name of the template
• attribute – the name of the variable of macro to access

配置

class flask.Config(root_path, defaults=None)

Works exactly like a dict but provides ways to fill it from files or special dictionaries. There are two common patterns to populate the config.

Either you can fill the config from a config file:

app.config.from_pyfile('yourconfig.cfg')

Or alternatively you can define the configuration options in the module that calls from_object() or provide an import path to a module that should be loaded. It is also possible to tell it to use the same module and with that provide the configuration values just before the call:

DEBUG = True
SECRET_KEY = 'development key'
app.config.from_object(__name__)

In both cases (loading from any Python file or loading from modules), only uppercase keys are added to the config. This makes it possible to use lowercase values in the config file for temporary values that are not added to the config or to define the config keys in the same file that implements the application.

Probably the most interesting way to load configurations is from an environment variable pointing to a file:

app.config.from_envvar('YOURAPPLICATION_SETTINGS')

In this case before launching the application you have to set this environment variable to the file you want to use. On Linux and OS X use the export statement:

export YOURAPPLICATION_SETTINGS='/path/to/config/file'

On windows use set instead.

参数:

• root_path – path to which files are read relative from. When the config object is created by the application, this is the application’s root_path.
• defaults – an optional dictionary of default values

from_envvar(variable_name, silent=False)

Loads a configuration from an environment variable pointing to a configuration file. This is basically just a shortcut with nicer error messages for this line of code:

app.config.from_pyfile(os.environ['YOURAPPLICATION_SETTINGS'])

参数:

• variable_name – name of the environment variable
• silent – set to True if you want silent failure for missing files.

返回:

bool. True if able to load config, False otherwise.

from_object(obj)

Updates the values from the given object. An object can be of one of the following two types:

• a string: in this case the object with that name will be imported
• an actual object reference: that object is used directly

Objects are usually either modules or classes.

Just the uppercase variables in that object are stored in the config. Example usage:

app.config.from_object('yourapplication.default_config')
from yourapplication import default_config
app.config.from_object(default_config)

You should not use this function to load the actual configuration but rather configuration defaults. The actual config should be loaded with from_pyfile() and ideally from a location not within the package because the package might be installed system wide.

参数:obj – an import name or object

from_pyfile(filename, silent=False)

Updates the values in the config from a Python file. This function behaves as if the file was imported as module with the from_object() function.

参数:

• filename – the filename of the config. This can either be an absolute filename or a filename relative to the root path.
• silent – set to True if you want silent failure for missing files.

0.7 新版功能: silent parameter.

扩展

flask.ext

这个模块重定向导入模块到 Flask 扩展。它在 0.8 中被加入，作为导入 Flask 扩展的权威方式，并使得我们在发布扩展时能有更大的灵活性。

如果你想使用名为 “Flask-Foo” 的扩展，你应按照下述从 ext 导入:

from flask.ext import foo

0.8 新版功能.

流的辅助函数

flask.stream_with_context(generator_or_function)

Request contexts disappear when the response is started on the server. This is done for efficiency reasons and to make it less likely to encounter memory leaks with badly written WSGI middlewares. The downside is that if you are using streamed responses, the generator cannot access request bound information any more.

This function however can help you keep the context around for longer:

from flask import stream_with_context, request, Response

@app.route('/stream')
def streamed_response():
    @stream_with_context
    def generate():
        yield 'Hello '
        yield request.args['name']
        yield '!'
    return Response(generate())

Alternatively it can also be used around a specific generator:

from flask import stream_with_context, request, Response

@app.route('/stream')
def streamed_response():
    def generate():
        yield 'Hello '
        yield request.args['name']
        yield '!'
    return Response(stream_with_context(generate()))

0.9 新版功能.

有用的内构件

class flask.ctx.RequestContext(app, environ, request=None)

The request context contains all request relevant information. It is created at the beginning of the request and pushed to the _request_ctx_stack and removed at the end of it. It will create the URL adapter and request object for the WSGI environment provided.

Do not attempt to use this class directly, instead use test_request_context() and request_context() to create this object.

When the request context is popped, it will evaluate all the functions registered on the application for teardown execution (teardown_request()).

The request context is automatically popped at the end of the request for you. In debug mode the request context is kept around if exceptions happen so that interactive debuggers have a chance to introspect the data. With 0.4 this can also be forced for requests that did not fail and outside of DEBUG mode. By setting 'flask._preserve_context' to True on the WSGI environment the context will not pop itself at the end of the request. This is used by the test_client() for example to implement the deferred cleanup functionality.

You might find this helpful for unittests where you need the information from the context local around for a little longer. Make sure to properly pop() the stack yourself in that situation, otherwise your unittests will leak memory.

copy()

Creates a copy of this request context with the same request object. This can be used to move a request context to a different greenlet. Because the actual request object is the same this cannot be used to move a request context to a different thread unless access to the request object is locked.

0.10 新版功能.

match_request()

Can be overridden by a subclass to hook into the matching of the request.

pop(exc=None)

Pops the request context and unbinds it by doing that. This will also trigger the execution of functions registered by the teardown_request() decorator.

在 0.9 版更改: Added the exc argument.

push()

Binds the request context to the current context.

flask._request_ctx_stack

Flask 中使用的所有的上下文局部对象，都由内部的 LocalStack 实现。这是一个带文档的实例，并且可以 在扩展和应用的代码中使用，但一般来说是不推荐这样使用的。

下面的属性在栈的每层上都存在:

app

活动的 Flask 应用

url_adapter

用于匹配请求的 URL 适配器

request

当前的请求对象

session

当前的会话对象

g

拥有 flask.g 对象上全部属性的对象

flashes

闪现消息的内部缓存

用法示例:

from flask import _request_ctx_stack

def get_session():
    ctx = _request_ctx_stack.top
    if ctx is not None:
        return ctx.session

class flask.ctx.AppContext(app)

The application context binds an application object implicitly to the current thread or greenlet, similar to how the RequestContext binds request information. The application context is also implicitly created if a request context is created but the application is not on top of the individual application context.

pop(exc=None)

Pops the app context.

push()

Binds the app context to the current context.

flask._app_ctx_stack

类似请求上下文，但是只跟应用绑定。主要为扩展提供数据存储。

0.9 新版功能.

class flask.blueprints.BlueprintSetupState(blueprint, app, options, first_registration)

Temporary holder object for registering a blueprint with the application. An instance of this class is created by the make_setup_state() method and later passed to all register callback functions.

add_url_rule(rule, endpoint=None, view_func=None, **options)

A helper method to register a rule (and optionally a view function) to the application. The endpoint is automatically prefixed with the blueprint’s name.

app = None

a reference to the current application

blueprint = None

a reference to the blueprint that created this setup state.

first_registration = None

as blueprints can be registered multiple times with the application and not everything wants to be registered multiple times on it, this attribute can be used to figure out if the blueprint was registered in the past already.

options = None

a dictionary with all options that were passed to the register_blueprint() method.

subdomain = None

The subdomain that the blueprint should be active for, None otherwise.

url_defaults = None

A dictionary with URL defaults that is added to each and every URL that was defined with the blueprint.

url_prefix = None

The prefix that should be used for all URLs defined on the blueprint.

信号

0.6 新版功能.

flask.signals_available

当信号系统可用时为 True ，即在 blinker 已经被安装的情况下。

flask.template_rendered

当一个模板成功渲染的时候，这个信号会发出。这个信号带着一个模板实例 template 和为一个字典的上下文（叫 context ）两个参数被调用。

flask.request_started

这个信号在处建立请求上下文之外的任何请求处理开始前发送。因为请求上下文 这个信号在任何对请求的处理前发送，但是正好是在请求的上下文被建立的时候。 因为请求上下文已经被约束了，用户可以使用 request 之类的标 准全局代理访问请求对象。

flask.request_finished

这个信号恰好在请求发送给客户端之前发送。它传递名为 response 的将被发送 的响应。

flask.got_request_exception

这个信号在请求处理中抛出异常时发送。它在标准异常处理生效 之前 ，甚至是 在不会处理异常的调试模式下也是如此。这个异常会被将作为一个 exception 传递到用户那。

flask.request_tearing_down

这个信号在请求销毁时发送。它总会被调用，即使发生异常。在这种清况下，造 成teardown的异常将会通过一个叫 exc 的关键字参数传递出来。

在 0.9 版更改: 添加了 exc 参数

flask.appcontext_tearing_down

这个信号在应用上下文销毁时发送。它总会被调用，即使发生异常。在这种清况 下，造成teardown的异常将会通过一个叫 exc 的关键字参数传递出来。发送 者是application对象。

flask.appcontext_pushed

当应用上下文被压入栈后会发送这个信号。发送者是application对象

0.10 新版功能.

flask.appcontext_popped

当应用上下文出栈后会发送这个信号。发送者是application对象。这常常与 appcontext_tearing_down 这个信号一致。

0.10 新版功能.

flask.message_flashed

This signal is sent when the application is flashing a message. The messages is sent as message keyword argument and the 当闪现一个消息时会发送这个信号。消息的内容将以 message 关键字参数 发送，而消息的种类则是 category 关键字参数。

0.10 新版功能.

class flask.signals.Namespace

blinker.base.Namespace 的别名，如果 blinker 可用的话。否则， 是一个发送伪信号的伪造的类。这个类对想提供与 Flask 相同的备用系统的 Flask扩展有用。

signal(name, doc=None)

在此命名空间中创建一个新信号，如果 blinker 可用的话。否则返回一个 带有不做任何事的发送方法，任何操作都会（包括连接）报错为 RuntimeError 的伪信号。

基于类的视图

0.7 新版功能.

class flask.views.View

Alternative way to use view functions. A subclass has to implement dispatch_request() which is called with the view arguments from the URL routing system. If methods is provided the methods do not have to be passed to the add_url_rule() method explicitly:

class MyView(View):
    methods = ['GET']

    def dispatch_request(self, name):
        return 'Hello %s!' % name

app.add_url_rule('/hello/<name>', view_func=MyView.as_view('myview'))

When you want to decorate a pluggable view you will have to either do that when the view function is created (by wrapping the return value of as_view()) or you can use the decorators attribute:

class SecretView(View):
    methods = ['GET']
    decorators = [superuser_required]

    def dispatch_request(self):
        ...

The decorators stored in the decorators list are applied one after another when the view function is created. Note that you can not use the class based decorators since those would decorate the view class and not the generated view function!

classmethod as_view(name, *class_args, **class_kwargs)

Converts the class into an actual view function that can be used with the routing system. Internally this generates a function on the fly which will instantiate the View on each request and call the dispatch_request() method on it.

The arguments passed to as_view() are forwarded to the constructor of the class.

decorators = []

The canonical way to decorate class-based views is to decorate the return value of as_view(). However since this moves parts of the logic from the class declaration to the place where it’s hooked into the routing system.

You can place one or more decorators in this list and whenever the view function is created the result is automatically decorated.

0.8 新版功能.

dispatch_request()

Subclasses have to override this method to implement the actual view function code. This method is called with all the arguments from the URL rule.

methods = None

A for which methods this pluggable view can handle.

class flask.views.MethodView

Like a regular class-based view but that dispatches requests to particular methods. For instance if you implement a method called get() it means you will response to 'GET' requests and the dispatch_request() implementation will automatically forward your request to that. Also options is set for you automatically:

class CounterAPI(MethodView):

    def get(self):
        return session.get('counter', 0)

    def post(self):
        session['counter'] = session.get('counter', 0) + 1
        return 'OK'

app.add_url_rule('/counter', view_func=CounterAPI.as_view('counter'))

URL 路由注册

在路由系统中定义规则可以的方法可以概括为三种:

1. 使用 flask.Flask.route() 装饰器
2. 使用 flask.Flask.add_url_rule() 函数
3. 直接访问暴露为 flask.Flask.url_map 的底层的 Werkzeug 路由系统

路由中的变量部分可以用尖括号指定（ /user/<username>）。默认情况下，URL 中的变量部分接受任何不带斜线的字符串，而 <converter:name> 也可以指定不 同的转换器。

变量部分以关键字参数传递给视图函数。

下面的转换器是可用的:

string	接受任何不带斜线的字符串（默认的转换器）
int	接受整数
float	同 int ，但是接受浮点数
path	和默认的相似，但也接受斜线

这里是一些例子:

@app.route('/')
def index():
    pass

@app.route('/<username>')
def show_user(username):
    pass

@app.route('/post/<int:post_id>')
def show_post(post_id):
    pass

需要注意的一个重要细节是 Flask 处理结尾斜线的方式。你可以应用下面两个 规则来保证 URL 的唯一:

1. 如果规则以斜线结尾，当用户以不带斜线的形式请求，用户被自动重定向到 带有结尾斜线的相同页面。
2. 如果规则结尾没有斜线，当用户以带斜线的形式请求，会抛出一个 404 not found 。

这与 web 服务器处理静态文件的方式一致。这使得安全地使用相对链接地址成为 可能。

你可以为同一个函数定义多个规则。无论如何，他们也要唯一。也可以给定默认值。 这里给出一个接受可选页面的 URL 定义:

@app.route('/users/', defaults={'page': 1})
@app.route('/users/page/<int:page>')
def show_users(page):
    pass

这指定了 /users/ 为第一页的 URL ，/users/page/N 为第 N 页的 URL 。

以下是 route() 和 add_url_rule() 接受的参数。两者唯一的区别是，带有路由参数的视图函数用装饰器定义，而不是 view_func 参数。

rule	URL 规则的字符串
endpoint	注册的 URL 规则的末端。如果没有显式地规定，Flask 本身假设 末端的名称是视图函数的名称，。
view_func	当请求呈递到给定的末端时调用的函数。如果没有提供，可以 在用在 view_functions 字典中以末端 作为键名存储，来在之后设定函数。
defaults	规则默认值的字典。上面的示例介绍了默认值如何工作。
subdomain	当使用子域名匹配的时候，为子域名设定规则。如果没有给定，假 定为默认的子域名。
**options	这些选项会被推送给底层的 Rule 对象。一个 Werkzeug 的变化是 method 选项的处理。methods是 这个规则被限定的方法列表（ GET ， POST 等等）。默认情 况下，规则只监听 GET （也隐式地监听 HEAD ）。从 Flask 0.6 开始，OPTIONS 也被隐式地加入，并且做标准的请求处理。 它们需要作为关键字参数来给定。

视图函数选项

对内部使用，视图函数可以有一些属性，附加到视图函数通常没有控制权的自定义的 行为。下面的可选属性覆盖 add_url_rule() 的默认值或一般 行为:

• __name__: 函数的名称默认用于末端。如果显式地提供末端，这个值会使用。 此外，它默认以蓝图的名称作为前缀，并且不能从函数本身自定义。
• methods: 如果没有在添加 URL 规则时提供 methods 参数。 Flask 会在视 图函数对象上寻找是否存在 methods 属性。如果存在，它会从上面拉取方法 的信息。
• provide_automatic_options: 如果设置了这个属性， Flask 会强制禁用或 启用 HTTP OPTIONS 响应的自动实现。这对于对单个视图自定义 OPTIONS 响应而使用装饰器的情况下是有用的。
• required_methods: 如果这个属性被设置了， 当注册一个 URL 规则的时候， Flask 将总是会添加这些 methods 即使 methods 参数在 route() 调用 的时候被显式的覆盖了。

完整的例子:

def index():
    if request.method == 'OPTIONS':
        # custom options handling here
        ...
    return 'Hello World!'
index.provide_automatic_options = False
index.methods = ['GET', 'OPTIONS']

app.add_url_rule('/', index)

0.8 新版功能: 加入了 provide_automatic_options 功能。