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avoid extra call from helpers.url_for
update changelog for method moves
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@davidism @pgjones @chrisngyn @ThiefMaster @jab @YKo20010 @Yourun-proger @raymond-devries @Jalkhov @pcorpet @laggardkernel @kevinanew
import functools
import inspect
import logging
import os
import sys
import typing as t
import weakref
from datetime import timedelta
from itertools import chain
from threading import Lock
from types import TracebackType
from werkzeug.datastructures import Headers
from werkzeug.datastructures import ImmutableDict
from werkzeug.exceptions import Aborter
from werkzeug.exceptions import BadRequest
from werkzeug.exceptions import BadRequestKeyError
from werkzeug.exceptions import HTTPException
from werkzeug.exceptions import InternalServerError
from werkzeug.routing import BuildError
from werkzeug.routing import Map
from werkzeug.routing import MapAdapter
from werkzeug.routing import RequestRedirect
from werkzeug.routing import RoutingException
from werkzeug.routing import Rule
from werkzeug.urls import url_quote
from werkzeug.utils import redirect as _wz_redirect
from werkzeug.wrappers import Response as BaseResponse
from . import cli
from . import json
from .config import Config
from .config import ConfigAttribute
from .ctx import _AppCtxGlobals
from .ctx import AppContext
from .ctx import RequestContext
from .globals import _app_ctx_stack
from .globals import _request_ctx_stack
from .globals import g
from .globals import request
from .globals import session
from .helpers import _split_blueprint_path
from .helpers import get_debug_flag
from .helpers import get_env
from .helpers import get_flashed_messages
from .helpers import get_load_dotenv
from .helpers import locked_cached_property
from .json import jsonify
from .logging import create_logger
from .scaffold import _endpoint_from_view_func
from .scaffold import _sentinel
from .scaffold import find_package
from .scaffold import Scaffold
from .scaffold import setupmethod
from .sessions import SecureCookieSessionInterface
from .sessions import SessionInterface
from .signals import appcontext_tearing_down
from .signals import got_request_exception
from .signals import request_finished
from .signals import request_started
from .signals import request_tearing_down
from .templating import DispatchingJinjaLoader
from .templating import Environment
from .typing import BeforeFirstRequestCallable
from .typing import ResponseReturnValue
from .typing import TeardownCallable
from .typing import TemplateFilterCallable
from .typing import TemplateGlobalCallable
from .typing import TemplateTestCallable
from .wrappers import Request
from .wrappers import Response
if t.TYPE_CHECKING: # pragma: no cover
import typing_extensions as te
from .blueprints import Blueprint
from .testing import FlaskClient
from .testing import FlaskCliRunner
from .typing import ErrorHandlerCallable
if sys.version_info >= (3, 8):
iscoroutinefunction = inspect.iscoroutinefunction
def iscoroutinefunction(func: t.Any) -> bool:
while inspect.ismethod(func):
func = func.__func__
while isinstance(func, functools.partial):
func = func.func
return inspect.iscoroutinefunction(func)
def _make_timedelta(value: t.Optional[timedelta]) -> t.Optional[timedelta]:
if value is None or isinstance(value, timedelta):
return value
return timedelta(seconds=value)
class Flask(Scaffold):
"""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 :file:`` file inside) or a standard module (just a ``.py`` file).
For more information about resource loading, see :func:`open_resource`.
Usually you create a :class:`Flask` instance in your main module or
in the :file:`` file of your package like this::
from flask import Flask
app = Flask(__name__)
.. admonition:: About the First Parameter
The idea of the first parameter is to give Flask an idea of what
belongs to your application. This name is used to find resources
on the filesystem, 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 :file:`yourapplication/`
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 `` and not
.. versionadded:: 0.7
The `static_url_path`, `static_folder`, and `template_folder`
parameters were added.
.. versionadded:: 0.8
The `instance_path` and `instance_relative_config` parameters were
.. versionadded:: 0.11
The `root_path` parameter was added.
.. versionadded:: 1.0
The ``host_matching`` and ``static_host`` parameters were added.
.. versionadded:: 1.0
The ``subdomain_matching`` parameter was added. Subdomain
matching needs to be enabled manually now. Setting
:data:`SERVER_NAME` does not implicitly enable it.
:param import_name: the name of the application package
:param 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.
:param static_folder: The folder with static files that is served at
``static_url_path``. Relative to the application ``root_path``
or an absolute path. Defaults to ``'static'``.
:param static_host: the host to use when adding the static route.
Defaults to None. Required when using ``host_matching=True``
with a ``static_folder`` configured.
:param host_matching: set ``url_map.host_matching`` attribute.
Defaults to False.
:param subdomain_matching: consider the subdomain relative to
:data:`SERVER_NAME` when matching routes. Defaults to False.
:param 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
:param 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
:param 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.
:param root_path: The path to the root of the application files.
This should only be set manually when it can't be detected
automatically, such as for namespace packages.
#: The class that is used for request objects. See :class:`~flask.Request`
#: for more information.
request_class = Request
#: The class that is used for response objects. See
#: :class:`~flask.Response` for more information.
response_class = Response
#: The class of the object assigned to :attr:`aborter`, created by
#: :meth:`create_aborter`. That object is called by
#: :func:`flask.abort` to raise HTTP errors, and can be
#: called directly as well.
#: Defaults to :class:`werkzeug.exceptions.Aborter`.
#: .. versionadded:: 2.2
aborter_class = Aborter
#: The class that is used for the Jinja environment.
#: .. versionadded:: 0.11
jinja_environment = Environment
#: The class that is used for the :data:`~flask.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 unexpected 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 :attr:`app_ctx_globals_class` because the
#: flask.g object is now application context scoped.
#: .. versionadded:: 0.10
app_ctx_globals_class = _AppCtxGlobals
#: The class that is used for the ``config`` attribute of this app.
#: Defaults to :class:`~flask.Config`.
#: Example use cases for a custom class:
#: 1. Default values for certain config options.
#: 2. Access to config values through attributes in addition to keys.
#: .. versionadded:: 0.11
config_class = Config
#: 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 test 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``.
testing = ConfigAttribute("TESTING")
#: 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
#: :data:`SECRET_KEY` configuration key. Defaults to ``None``.
secret_key = ConfigAttribute("SECRET_KEY")
#: 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_cookie_name = ConfigAttribute("SESSION_COOKIE_NAME")
#: A :class:`~datetime.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)``
permanent_session_lifetime = ConfigAttribute(
"PERMANENT_SESSION_LIFETIME", get_converter=_make_timedelta
#: A :class:`~datetime.timedelta` or number of seconds which is used
#: as the default ``max_age`` for :func:`send_file`. The default is
#: ``None``, which tells the browser to use conditional requests
#: instead of a timed cache.
#: Configured with the :data:`SEND_FILE_MAX_AGE_DEFAULT`
#: configuration key.
#: .. versionchanged:: 2.0
#: Defaults to ``None`` instead of 12 hours.
send_file_max_age_default = ConfigAttribute(
"SEND_FILE_MAX_AGE_DEFAULT", get_converter=_make_timedelta
#: 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 :func:`send_file` method.
#: .. versionadded:: 0.2
#: This attribute can also be configured from the config with the
#: ``USE_X_SENDFILE`` configuration key. Defaults to ``False``.
use_x_sendfile = ConfigAttribute("USE_X_SENDFILE")
#: The JSON encoder class to use. Defaults to :class:`~flask.json.JSONEncoder`.
#: .. versionadded:: 0.10
json_encoder = json.JSONEncoder
#: The JSON decoder class to use. Defaults to :class:`~flask.json.JSONDecoder`.
#: .. versionadded:: 0.10
json_decoder = json.JSONDecoder
#: Options that are passed to the Jinja environment in
#: :meth:`create_jinja_environment`. Changing these options after
#: the environment is created (accessing :attr:`jinja_env`) will
#: have no effect.
#: .. versionchanged:: 1.1.0
#: This is a ``dict`` instead of an ``ImmutableDict`` to allow
#: easier configuration.
jinja_options: dict = {}
#: Default configuration parameters.
default_config = ImmutableDict(
"ENV": None,
"DEBUG": None,
"TESTING": False,
"PERMANENT_SESSION_LIFETIME": timedelta(days=31),
"JSONIFY_MIMETYPE": "application/json",
#: The rule object to use for URL rules created. This is used by
#: :meth:`add_url_rule`. Defaults to :class:`werkzeug.routing.Rule`.
#: .. versionadded:: 0.7
url_rule_class = Rule
#: The map object to use for storing the URL rules and routing
#: configuration parameters. Defaults to :class:`werkzeug.routing.Map`.
#: .. versionadded:: 1.1.0
url_map_class = Map
#: The :meth:`test_client` method creates an instance of this test
#: client class. Defaults to :class:`~flask.testing.FlaskClient`.
#: .. versionadded:: 0.7
test_client_class: t.Optional[t.Type["FlaskClient"]] = None
#: The :class:`~click.testing.CliRunner` subclass, by default
#: :class:`~flask.testing.FlaskCliRunner` that is used by
#: :meth:`test_cli_runner`. Its ``__init__`` method should take a
#: Flask app object as the first argument.
#: .. versionadded:: 1.0
test_cli_runner_class: t.Optional[t.Type["FlaskCliRunner"]] = None
#: the session interface to use. By default an instance of
#: :class:`~flask.sessions.SecureCookieSessionInterface` is used here.
#: .. versionadded:: 0.8
session_interface: SessionInterface = SecureCookieSessionInterface()
def __init__(
import_name: str,
static_url_path: t.Optional[str] = None,
static_folder: t.Optional[t.Union[str, os.PathLike]] = "static",
static_host: t.Optional[str] = None,
host_matching: bool = False,
subdomain_matching: bool = False,
template_folder: t.Optional[str] = "templates",
instance_path: t.Optional[str] = None,
instance_relative_config: bool = False,
root_path: t.Optional[str] = None,
if instance_path is None:
instance_path = self.auto_find_instance_path()
elif not os.path.isabs(instance_path):
raise ValueError(
"If an instance path is provided it must be absolute."
" A relative path was given instead."
#: Holds the path to the instance folder.
#: .. versionadded:: 0.8
self.instance_path = instance_path
#: The configuration dictionary as :class:`Config`. This behaves
#: exactly like a regular dictionary but supports additional methods
#: to load a config from files.
self.config = self.make_config(instance_relative_config)
#: An instance of :attr:`aborter_class` created by
#: :meth:`make_aborter`. This is called by :func:`flask.abort`
#: to raise HTTP errors, and can be called directly as well.
#: .. versionadded:: 2.2
#: Moved from ``flask.abort``, which calls this object.
self.aborter = self.make_aborter()
#: A list of functions that are called by
#: :meth:`handle_url_build_error` when :meth:`.url_for` raises a
#: :exc:`~werkzeug.routing.BuildError`. Each function is called
#: with ``error``, ``endpoint`` and ``values``. If a function
#: returns ``None`` or raises a ``BuildError``, it is skipped.
#: Otherwise, its return value is returned by ``url_for``.
#: .. versionadded:: 0.9
self.url_build_error_handlers: t.List[
t.Callable[[Exception, str, t.Dict[str, t.Any]], str]
] = []
#: A list of functions that will be called at the beginning of the
#: first request to this instance. To register a function, use the
#: :meth:`before_first_request` decorator.
#: .. versionadded:: 0.8
self.before_first_request_funcs: t.List[BeforeFirstRequestCallable] = []
#: 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.
#: .. versionadded:: 0.9
self.teardown_appcontext_funcs: t.List[TeardownCallable] = []
#: A list of shell context processor functions that should be run
#: when a shell context is created.
#: .. versionadded:: 0.11
self.shell_context_processors: t.List[t.Callable[[], t.Dict[str, t.Any]]] = []
#: Maps registered blueprint names to blueprint objects. The
#: dict retains the order the blueprints were registered in.
#: Blueprints can be registered multiple times, this dict does
#: not track how often they were attached.
#: .. versionadded:: 0.7
self.blueprints: t.Dict[str, "Blueprint"] = {}
#: a place where extensions can store application specific state. For
#: example this is where an extension could store database engines and
#: similar things.
#: The key must match the name of the extension module. For example in
#: case of a "Flask-Foo" extension in `flask_foo`, the key would be
#: ``'foo'``.
#: .. versionadded:: 0.7
self.extensions: dict = {}
#: The :class:`~werkzeug.routing.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(super(ListConverter, self).to_url(value)
#: for value in values)
#: app = Flask(__name__)
#: app.url_map.converters['list'] = ListConverter
self.url_map = self.url_map_class()
self.url_map.host_matching = host_matching
self.subdomain_matching = subdomain_matching
# tracks internally if the application already handled at least one
# request.
self._got_first_request = False
self._before_request_lock = Lock()
# Add a static route using the provided static_url_path, static_host,
# and static_folder if there is a configured static_folder.
# Note we do this without checking if static_folder exists.
# For one, it might be created while the server is running (e.g. during
# development). Also, Google App Engine stores static files somewhere
if self.has_static_folder:
assert (
bool(static_host) == host_matching
), "Invalid static_host/host_matching combination"
# Use a weakref to avoid creating a reference cycle between the app
# and the view function (see #3761).
self_ref = weakref.ref(self)
view_func=lambda **kw: self_ref().send_static_file(**kw), # type: ignore # noqa: B950
# Set the name of the Click group in case someone wants to add
# the app's commands to another CLI tool. =
def _is_setup_finished(self) -> bool:
return self.debug and self._got_first_request
def name(self) -> str: # type: ignore
"""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.
.. versionadded:: 0.8
if self.import_name == "__main__":
fn = getattr(sys.modules["__main__"], "__file__", None)
if fn is None:
return "__main__"
return os.path.splitext(os.path.basename(fn))[0]
return self.import_name
def propagate_exceptions(self) -> bool:
"""Returns the value of the ``PROPAGATE_EXCEPTIONS`` configuration
value in case it's set, otherwise a sensible default is returned.
.. versionadded:: 0.7
rv = self.config["PROPAGATE_EXCEPTIONS"]
if rv is not None:
return rv
return self.testing or self.debug
def preserve_context_on_exception(self) -> bool:
"""Returns the value of the ``PRESERVE_CONTEXT_ON_EXCEPTION``
configuration value in case it's set, otherwise a sensible default
is returned.
.. versionadded:: 0.7
if rv is not None:
return rv
return self.debug
def logger(self) -> logging.Logger:
"""A standard Python :class:`~logging.Logger` for the app, with
the same name as :attr:`name`.
In debug mode, the logger's :attr:`~logging.Logger.level` will
be set to :data:`~logging.DEBUG`.
If there are no handlers configured, a default handler will be
added. See :doc:`/logging` for more information.
.. versionchanged:: 1.1.0
The logger takes the same name as :attr:`name` rather than
hard-coding ``""``.
.. versionchanged:: 1.0.0
Behavior was simplified. The logger is always named
``""``. The level is only set during configuration,
it doesn't check ``app.debug`` each time. Only one format is
used, not different ones depending on ``app.debug``. No
handlers are removed, and a handler is only added if no
handlers are already configured.
.. versionadded:: 0.3
return create_logger(self)
def jinja_env(self) -> Environment:
"""The Jinja environment used to load templates.
The environment is created the first time this property is
accessed. Changing :attr:`jinja_options` after that will have no
return self.create_jinja_environment()
def got_first_request(self) -> bool:
"""This attribute is set to ``True`` if the application started
handling the first request.
.. versionadded:: 0.8
return self._got_first_request
def make_config(self, instance_relative: bool = False) -> Config:
"""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.
.. versionadded:: 0.8
root_path = self.root_path
if instance_relative:
root_path = self.instance_path
defaults = dict(self.default_config)
defaults["ENV"] = get_env()
defaults["DEBUG"] = get_debug_flag()
return self.config_class(root_path, defaults)
def make_aborter(self) -> Aborter:
"""Create the object to assign to :attr:`aborter`. That object
is called by :func:`flask.abort` to raise HTTP errors, and can
be called directly as well.
By default, this creates an instance of :attr:`aborter_class`,
which defaults to :class:`werkzeug.exceptions.Aborter`.
.. versionadded:: 2.2
return self.aborter_class()
def auto_find_instance_path(self) -> str:
"""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.
.. versionadded:: 0.8
prefix, package_path = find_package(self.import_name)
if prefix is None:
return os.path.join(package_path, "instance")
return os.path.join(prefix, "var", f"{}-instance")
def open_instance_resource(self, resource: str, mode: str = "rb") -> t.IO[t.AnyStr]:
"""Opens a resource from the application's instance folder
(:attr:`instance_path`). Otherwise works like
:meth:`open_resource`. Instance resources can also be opened for
:param resource: the name of the resource. To access resources within
subfolders use forward slashes as separator.
:param mode: resource file opening mode, default is 'rb'.
return open(os.path.join(self.instance_path, resource), mode)
def templates_auto_reload(self) -> bool:
"""Reload templates when they are changed. Used by
This attribute can be configured with :data:`TEMPLATES_AUTO_RELOAD`. If
not set, it will be enabled in debug mode.
.. versionadded:: 1.0
This property was added but the underlying config and behavior
already existed.
rv = self.config["TEMPLATES_AUTO_RELOAD"]
return rv if rv is not None else self.debug
def templates_auto_reload(self, value: bool) -> None:
self.config["TEMPLATES_AUTO_RELOAD"] = value
def create_jinja_environment(self) -> Environment:
"""Create the Jinja environment based on :attr:`jinja_options`
and the various Jinja-related methods of the app. Changing
:attr:`jinja_options` after this will have no effect. Also adds
Flask-related globals and filters to the environment.
.. versionchanged:: 0.11
``Environment.auto_reload`` set in accordance with
``TEMPLATES_AUTO_RELOAD`` configuration option.
.. versionadded:: 0.5
options = dict(self.jinja_options)
if "autoescape" not in options:
options["autoescape"] = self.select_jinja_autoescape
if "auto_reload" not in options:
options["auto_reload"] = self.templates_auto_reload
rv = self.jinja_environment(self, **options)
# request, session and g are normally added with the
# context processor for efficiency reasons but for imported
# templates we also want the proxies in there.
rv.policies["json.dumps_function"] = json.dumps
return rv
def create_global_jinja_loader(self) -> DispatchingJinjaLoader:
"""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 :meth:`jinja_loader` function instead.
The global loader dispatches between the loaders of the application
and the individual blueprints.
.. versionadded:: 0.7
return DispatchingJinjaLoader(self)
def select_jinja_autoescape(self, filename: str) -> bool:
"""Returns ``True`` if autoescaping should be active for the given
template name. If no template name is given, returns `True`.
.. versionadded:: 0.5
if filename is None:
return True
return filename.endswith((".html", ".htm", ".xml", ".xhtml"))
def update_template_context(self, context: dict) -> None:
"""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.
:param context: the context as a dictionary that is updated in place
to add extra variables.
names: t.Iterable[t.Optional[str]] = (None,)
# A template may be rendered outside a request context.
if request:
names = chain(names, reversed(request.blueprints))
# The values passed to render_template take precedence. Keep a
# copy to re-apply after all context functions.
orig_ctx = context.copy()
for name in names:
if name in self.template_context_processors:
for func in self.template_context_processors[name]:
def make_shell_context(self) -> dict:
"""Returns the shell context for an interactive shell for this
application. This runs all the registered shell context
.. versionadded:: 0.11
rv = {"app": self, "g": g}
for processor in self.shell_context_processors:
return rv
#: What environment the app is running in. Flask and extensions may
#: enable behaviors based on the environment, such as enabling debug
#: mode. This maps to the :data:`ENV` config key. This is set by the
#: :envvar:`FLASK_ENV` environment variable and may not behave as
#: expected if set in code.
#: **Do not enable development when deploying in production.**
#: Default: ``'production'``
env = ConfigAttribute("ENV")
def debug(self) -> bool:
"""Whether debug mode is enabled. When using ``flask run`` to start
the development server, an interactive debugger will be shown for
unhandled exceptions, and the server will be reloaded when code
changes. This maps to the :data:`DEBUG` config key. This is
enabled when :attr:`env` is ``'development'`` and is overridden
by the ``FLASK_DEBUG`` environment variable. It may not behave as
expected if set in code.
**Do not enable debug mode when deploying in production.**
Default: ``True`` if :attr:`env` is ``'development'``, or
``False`` otherwise.
return self.config["DEBUG"]
def debug(self, value: bool) -> None:
self.config["DEBUG"] = value
self.jinja_env.auto_reload = self.templates_auto_reload
def run(
host: t.Optional[str] = None,
port: t.Optional[int] = None,
debug: t.Optional[bool] = None,
load_dotenv: bool = True,
**options: t.Any,
) -> None:
"""Runs the application on a local development server.
Do not use ``run()`` in a production setting. It is not intended to
meet security and performance requirements for a production server.
Instead, see :doc:`/deploying/index` for WSGI server recommendations.
If the :attr:`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.
It is not recommended to use this function for development with
automatic reloading as this is badly supported. Instead you should
be using the :command:`flask` command line script's ``run`` support.
.. admonition:: 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 :meth:`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
:param host: the hostname to listen on. Set this to ``''`` to
have the server available externally as well. Defaults to
``''`` or the host in the ``SERVER_NAME`` config variable
if present.
:param port: the port of the webserver. Defaults to ``5000`` or the
port defined in the ``SERVER_NAME`` config variable if present.
:param debug: if given, enable or disable debug mode. See
:param load_dotenv: Load the nearest :file:`.env` and :file:`.flaskenv`
files to set environment variables. Will also change the working
directory to the directory containing the first file found.
:param options: the options to be forwarded to the underlying Werkzeug
server. See :func:`werkzeug.serving.run_simple` for more
.. versionchanged:: 1.0
If installed, python-dotenv will be used to load environment
variables from :file:`.env` and :file:`.flaskenv` files.
If set, the :envvar:`FLASK_ENV` and :envvar:`FLASK_DEBUG`
environment variables will override :attr:`env` and
Threaded mode is enabled by default.
.. versionchanged:: 0.10
The default port is now picked from the ``SERVER_NAME``
# Change this into a no-op if the server is invoked from the
# command line. Have a look at for more information.
if os.environ.get("FLASK_RUN_FROM_CLI") == "true":
from .debughelpers import explain_ignored_app_run
if get_load_dotenv(load_dotenv):
# if set, let env vars override previous values
if "FLASK_ENV" in os.environ:
self.env = get_env()
self.debug = get_debug_flag()
elif "FLASK_DEBUG" in os.environ:
self.debug = get_debug_flag()
# debug passed to method overrides all other sources
if debug is not None:
self.debug = bool(debug)
server_name = self.config.get("SERVER_NAME")
sn_host = sn_port = None
if server_name:
sn_host, _, sn_port = server_name.partition(":")
if not host:
if sn_host:
host = sn_host
host = ""
if port or port == 0:
port = int(port)
elif sn_port:
port = int(sn_port)
port = 5000
options.setdefault("use_reloader", self.debug)
options.setdefault("use_debugger", self.debug)
options.setdefault("threaded", True)
cli.show_server_banner(self.env, self.debug,, False)
from werkzeug.serving import run_simple
run_simple(t.cast(str, host), port, self, **options)
# reset the first request information if the development server
# reset normally. This makes it possible to restart the server
# without reloader and that stuff from an interactive shell.
self._got_first_request = False
def test_client(self, use_cookies: bool = True, **kwargs: t.Any) -> "FlaskClient":
"""Creates a test client for this application. For information
about unit testing head over to :doc:`/testing`.
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 :attr:`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'
Additionally, you may pass optional keyword arguments that will then
be passed to the application's :attr:`test_client_class` constructor.
For example::
from flask.testing import FlaskClient
class CustomClient(FlaskClient):
def __init__(self, *args, **kwargs):
self._authentication = kwargs.pop("authentication")
super(CustomClient,self).__init__( *args, **kwargs)
app.test_client_class = CustomClient
client = app.test_client(authentication='Basic ....')
See :class:`~flask.testing.FlaskClient` for more information.
.. versionchanged:: 0.4
added support for ``with`` block usage for the client.
.. versionadded:: 0.7
The `use_cookies` parameter was added as well as the ability
to override the client to be used by setting the
:attr:`test_client_class` attribute.
.. versionchanged:: 0.11
Added `**kwargs` to support passing additional keyword arguments to
the constructor of :attr:`test_client_class`.
cls = self.test_client_class
if cls is None:
from .testing import FlaskClient as cls # type: ignore
return cls( # type: ignore
self, self.response_class, use_cookies=use_cookies, **kwargs
def test_cli_runner(self, **kwargs: t.Any) -> "FlaskCliRunner":
"""Create a CLI runner for testing CLI commands.
See :ref:`testing-cli`.
Returns an instance of :attr:`test_cli_runner_class`, by default
:class:`~flask.testing.FlaskCliRunner`. The Flask app object is
passed as the first argument.
.. versionadded:: 1.0
cls = self.test_cli_runner_class
if cls is None:
from .testing import FlaskCliRunner as cls # type: ignore
return cls(self, **kwargs) # type: ignore
def register_blueprint(self, blueprint: "Blueprint", **options: t.Any) -> None:
"""Register a :class:`~flask.Blueprint` on the application. Keyword
arguments passed to this method will override the defaults set on the
Calls the blueprint's :meth:`~flask.Blueprint.register` method after
recording the blueprint in the application's :attr:`blueprints`.
:param blueprint: The blueprint to register.
:param url_prefix: Blueprint routes will be prefixed with this.
:param subdomain: Blueprint routes will match on this subdomain.
:param url_defaults: Blueprint routes will use these default values for
view arguments.
:param options: Additional keyword arguments are passed to
:class:`~flask.blueprints.BlueprintSetupState`. They can be
accessed in :meth:`~flask.Blueprint.record` callbacks.
.. versionchanged:: 2.0.1
The ``name`` option can be used to change the (pre-dotted)
name the blueprint is registered with. This allows the same
blueprint to be registered multiple times with unique names
for ``url_for``.
.. versionadded:: 0.7
blueprint.register(self, options)
def iter_blueprints(self) -> t.ValuesView["Blueprint"]:
"""Iterates over all blueprints by the order they were registered.
.. versionadded:: 0.11
return self.blueprints.values()
def add_url_rule(
rule: str,
endpoint: t.Optional[str] = None,
view_func: t.Optional[t.Callable] = None,
provide_automatic_options: t.Optional[bool] = None,
**options: t.Any,
) -> None:
if endpoint is None:
endpoint = _endpoint_from_view_func(view_func) # type: ignore
options["endpoint"] = endpoint
methods = options.pop("methods", None)
# if the methods are not given and the view_func object knows its
# methods we can use that instead. If neither exists, we go with
# a tuple of only ``GET`` as default.
if methods is None:
methods = getattr(view_func, "methods", None) or ("GET",)
if isinstance(methods, str):
raise TypeError(
"Allowed methods must be a list of strings, for"
' example: @app.route(..., methods=["POST"])'
methods = {item.upper() for item in methods}
# Methods that should always be added
required_methods = set(getattr(view_func, "required_methods", ()))
# starting with Flask 0.8 the view_func object can disable and
# force-enable the automatic options handling.
if provide_automatic_options is None:
provide_automatic_options = getattr(
view_func, "provide_automatic_options", None
if provide_automatic_options is None:
if "OPTIONS" not in methods:
provide_automatic_options = True
provide_automatic_options = False
# Add the required methods now.
methods |= required_methods
rule = self.url_rule_class(rule, methods=methods, **options)
rule.provide_automatic_options = provide_automatic_options # type: ignore
if view_func is not None:
old_func = self.view_functions.get(endpoint)
if old_func is not None and old_func != view_func:
raise AssertionError(
"View function mapping is overwriting an existing"
f" endpoint function: {endpoint}"
self.view_functions[endpoint] = view_func
def template_filter(
self, name: t.Optional[str] = None
) -> t.Callable[[TemplateFilterCallable], TemplateFilterCallable]:
"""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::
def reverse(s):
return s[::-1]
:param name: the optional name of the filter, otherwise the
function name will be used.
def decorator(f: TemplateFilterCallable) -> TemplateFilterCallable:
self.add_template_filter(f, name=name)
return f
return decorator
def add_template_filter(
self, f: TemplateFilterCallable, name: t.Optional[str] = None
) -> None:
"""Register a custom template filter. Works exactly like the
:meth:`template_filter` decorator.
:param name: the optional name of the filter, otherwise the
function name will be used.
self.jinja_env.filters[name or f.__name__] = f
def template_test(
self, name: t.Optional[str] = None
) -> t.Callable[[TemplateTestCallable], TemplateTestCallable]:
"""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::
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
.. versionadded:: 0.10
:param name: the optional name of the test, otherwise the
function name will be used.
def decorator(f: TemplateTestCallable) -> TemplateTestCallable:
self.add_template_test(f, name=name)
return f
return decorator
def add_template_test(
self, f: TemplateTestCallable, name: t.Optional[str] = None
) -> None:
"""Register a custom template test. Works exactly like the
:meth:`template_test` decorator.
.. versionadded:: 0.10
:param name: the optional name of the test, otherwise the
function name will be used.
self.jinja_env.tests[name or f.__name__] = f
def template_global(
self, name: t.Optional[str] = None
) -> t.Callable[[TemplateGlobalCallable], TemplateGlobalCallable]:
"""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::
def double(n):
return 2 * n
.. versionadded:: 0.10
:param name: the optional name of the global function, otherwise the
function name will be used.
def decorator(f: TemplateGlobalCallable) -> TemplateGlobalCallable:
self.add_template_global(f, name=name)
return f
return decorator
def add_template_global(
self, f: TemplateGlobalCallable, name: t.Optional[str] = None
) -> None:
"""Register a custom template global function. Works exactly like the
:meth:`template_global` decorator.
.. versionadded:: 0.10
:param name: the optional name of the global function, otherwise the
function name will be used.
self.jinja_env.globals[name or f.__name__] = f
def before_first_request(
self, f: BeforeFirstRequestCallable
) -> BeforeFirstRequestCallable:
"""Registers a function to be run before the first request to this
instance of the application.
The function will be called without any arguments and its return
value is ignored.
.. versionadded:: 0.8
return f
def teardown_appcontext(self, f: TeardownCallable) -> TeardownCallable:
"""Registers a function to be called when the application context
ends. These functions are typically also called when the request
context is popped.
ctx = app.app_context()
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 unhandled exception
it will be passed an error object. If an :meth:`errorhandler` is
registered, it will handle the exception and the teardown will not
receive it.
The return values of teardown functions are ignored.
.. versionadded:: 0.9
return f
def shell_context_processor(self, f: t.Callable) -> t.Callable:
"""Registers a shell context processor function.
.. versionadded:: 0.11
return f
def _find_error_handler(self, e: Exception) -> t.Optional["ErrorHandlerCallable"]:
"""Return a registered error handler for an exception in this order:
blueprint handler for a specific code, app handler for a specific code,
blueprint handler for an exception class, app handler for an exception
class, or ``None`` if a suitable handler is not found.
exc_class, code = self._get_exc_class_and_code(type(e))
names = (*request.blueprints, None)
for c in (code, None) if code is not None else (None,):
for name in names:
handler_map = self.error_handler_spec[name][c]
if not handler_map:
for cls in exc_class.__mro__:
handler = handler_map.get(cls)
if handler is not None:
return handler
return None
def handle_http_exception(
self, e: HTTPException
) -> t.Union[HTTPException, ResponseReturnValue]:
"""Handles an HTTP exception. By default this will invoke the
registered error handlers and fall back to returning the
exception as response.
.. versionchanged:: 1.0.3
``RoutingException``, used internally for actions such as
slash redirects during routing, is not passed to error
.. versionchanged:: 1.0
Exceptions are looked up by code *and* by MRO, so
``HTTPException`` subclasses can be handled with a catch-all
handler for the base ``HTTPException``.
.. versionadded:: 0.3
# Proxy exceptions don't have error codes. We want to always return
# those unchanged as errors
if e.code is None:
return e
# RoutingExceptions are used internally to trigger routing
# actions, such as slash redirects raising RequestRedirect. They
# are not raised or handled in user code.
if isinstance(e, RoutingException):
return e
handler = self._find_error_handler(e)
if handler is None:
return e
return self.ensure_sync(handler)(e)
def trap_http_exception(self, e: Exception) -> bool:
"""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
.. versionchanged:: 1.0
Bad request errors are not trapped by default in debug mode.
.. versionadded:: 0.8
if self.config["TRAP_HTTP_EXCEPTIONS"]:
return True
trap_bad_request = self.config["TRAP_BAD_REQUEST_ERRORS"]
# if unset, trap key errors in debug mode
if (
trap_bad_request is None
and self.debug
and isinstance(e, BadRequestKeyError)
return True
if trap_bad_request:
return isinstance(e, BadRequest)
return False
def handle_user_exception(
self, e: Exception
) -> t.Union[HTTPException, ResponseReturnValue]:
"""This method is called whenever an exception occurs that
should be handled. A special case is :class:`~werkzeug
.exceptions.HTTPException` which is forwarded to the
:meth:`handle_http_exception` method. This function will either
return a response value or reraise the exception with the same
.. versionchanged:: 1.0
Key errors raised from request data like ``form`` show the
bad key in debug mode rather than a generic bad request
.. versionadded:: 0.7
if isinstance(e, BadRequestKeyError) and (
self.debug or self.config["TRAP_BAD_REQUEST_ERRORS"]
e.show_exception = True
if isinstance(e, HTTPException) and not self.trap_http_exception(e):
return self.handle_http_exception(e)
handler = self._find_error_handler(e)
if handler is None:
return self.ensure_sync(handler)(e)
def handle_exception(self, e: Exception) -> Response:
"""Handle an exception that did not have an error handler
associated with it, or that was raised from an error handler.
This always causes a 500 ``InternalServerError``.
Always sends the :data:`got_request_exception` signal.
If :attr:`propagate_exceptions` is ``True``, such as in debug
mode, the error will be re-raised so that the debugger can
display it. Otherwise, the original exception is logged, and
an :exc:`~werkzeug.exceptions.InternalServerError` is returned.
If an error handler is registered for ``InternalServerError`` or
``500``, it will be used. For consistency, the handler will
always receive the ``InternalServerError``. The original
unhandled exception is available as ``e.original_exception``.
.. versionchanged:: 1.1.0
Always passes the ``InternalServerError`` instance to the
handler, setting ``original_exception`` to the unhandled
.. versionchanged:: 1.1.0
``after_request`` functions and other finalization is done
even for the default 500 response when there is no handler.
.. versionadded:: 0.3
exc_info = sys.exc_info()
got_request_exception.send(self, exception=e)
if self.propagate_exceptions:
# Re-raise if called with an active exception, otherwise
# raise the passed in exception.
if exc_info[1] is e:
raise e
server_error: t.Union[InternalServerError, ResponseReturnValue]
server_error = InternalServerError(original_exception=e)
handler = self._find_error_handler(server_error)
if handler is not None:
server_error = self.ensure_sync(handler)(server_error)
return self.finalize_request(server_error, from_error_handler=True)
def log_exception(
exc_info: t.Union[
t.Tuple[type, BaseException, TracebackType], t.Tuple[None, None, None]
) -> None:
"""Logs an exception. This is called by :meth:`handle_exception`
if debugging is disabled and right before the handler is called.
The default implementation logs the exception as error on the
.. versionadded:: 0.8
f"Exception on {request.path} [{request.method}]", exc_info=exc_info
def raise_routing_exception(self, request: Request) -> "te.NoReturn":
"""Intercept routing exceptions and possibly do something else.
In debug mode, intercept a routing redirect and replace it with
an error if the body will be discarded.
With modern Werkzeug this shouldn't occur, since it now uses a
308 status which tells the browser to resend the method and
.. versionchanged:: 2.1
Don't intercept 307 and 308 redirects.
:meta private:
if (
not self.debug
or not isinstance(request.routing_exception, RequestRedirect)
or request.routing_exception.code in {307, 308}
or request.method in {"GET", "HEAD", "OPTIONS"}
raise request.routing_exception # type: ignore
from .debughelpers import FormDataRoutingRedirect
raise FormDataRoutingRedirect(request)
def dispatch_request(self) -> ResponseReturnValue:
"""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 :func:`make_response`.
.. versionchanged:: 0.7
This no longer does the exception handling, this code was
moved to the new :meth:`full_dispatch_request`.
req =
if req.routing_exception is not None:
rule = req.url_rule
# if we provide automatic options for this URL and the
# request came with the OPTIONS method, reply automatically
if (
getattr(rule, "provide_automatic_options", False)
and req.method == "OPTIONS"
return self.make_default_options_response()
# otherwise dispatch to the handler for that endpoint
return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
def full_dispatch_request(self) -> Response:
"""Dispatches the request and on top of that performs request
pre and postprocessing as well as HTTP exception catching and
error handling.
.. versionadded:: 0.7
rv = self.preprocess_request()
if rv is None:
rv = self.dispatch_request()
except Exception as e:
rv = self.handle_user_exception(e)
return self.finalize_request(rv)
def finalize_request(
rv: t.Union[ResponseReturnValue, HTTPException],
from_error_handler: bool = False,
) -> Response:
"""Given the return value from a view function this finalizes
the request by converting it into a response and invoking the
postprocessing functions. This is invoked for both normal
request dispatching as well as error handlers.
Because this means that it might be called as a result of a
failure a special safe mode is available which can be enabled
with the `from_error_handler` flag. If enabled, failures in
response processing will be logged and otherwise ignored.
response = self.make_response(rv)
response = self.process_response(response)
request_finished.send(self, response=response)
except Exception:
if not from_error_handler:
"Request finalizing failed with an error while handling an error"
return response
def try_trigger_before_first_request_functions(self) -> None:
"""Called before each request and will ensure that it triggers
the :attr:`before_first_request_funcs` and only exactly once per
application instance (which means process usually).
if self._got_first_request:
with self._before_request_lock:
if self._got_first_request:
for func in self.before_first_request_funcs:
self._got_first_request = True
def make_default_options_response(self) -> 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.
.. versionadded:: 0.7
adapter =
methods = adapter.allowed_methods()
rv = self.response_class()
return rv
def should_ignore_error(self, error: t.Optional[BaseException]) -> bool:
"""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.
.. versionadded:: 0.10
return False
def ensure_sync(self, func: t.Callable) -> t.Callable:
"""Ensure that the function is synchronous for WSGI workers.
Plain ``def`` functions are returned as-is. ``async def``
functions are wrapped to run and wait for the response.
Override this method to change how the app runs async views.
.. versionadded:: 2.0
if iscoroutinefunction(func):
return self.async_to_sync(func)
return func
def async_to_sync(
self, func: t.Callable[..., t.Coroutine]
) -> t.Callable[..., t.Any]:
"""Return a sync function that will run the coroutine function.
.. code-block:: python
result = app.async_to_sync(func)(*args, **kwargs)
Override this method to change how the app converts async code
to be synchronously callable.
.. versionadded:: 2.0
from asgiref.sync import async_to_sync as asgiref_async_to_sync
except ImportError:
raise RuntimeError(
"Install Flask with the 'async' extra in order to use async views."
) from None
return asgiref_async_to_sync(func)
def url_for(
endpoint: str,
_anchor: t.Optional[str] = None,
_method: t.Optional[str] = None,
_scheme: t.Optional[str] = None,
_external: t.Optional[bool] = None,
**values: t.Any,
) -> str:
"""Generate a URL to the given endpoint with the given values.
This is called by :func:`flask.url_for`, and can be called
directly as well.
An *endpoint* is the name of a URL rule, usually added with
:meth:`@app.route() <route>`, and usually the same name as the
view function. A route defined in a :class:`~flask.Blueprint`
will prepend the blueprint's name separated by a ``.`` to the
In some cases, such as email messages, you want URLs to include
the scheme and domain, like ````. When
not in an active request, URLs will be external by default, but
this requires setting :data:`SERVER_NAME` so Flask knows what
domain to use. :data:`APPLICATION_ROOT` and
:data:`PREFERRED_URL_SCHEME` should also be configured as
needed. This config is only used when not in an active request.
Functions can be decorated with :meth:`url_defaults` to modify
keyword arguments before the URL is built.
If building fails for some reason, such as an unknown endpoint
or incorrect values, the app's :meth:`handle_url_build_error`
method is called. If that returns a string, that is returned,
otherwise a :exc:`~werkzeug.routing.BuildError` is raised.
:param endpoint: The endpoint name associated with the URL to
generate. If this starts with a ``.``, the current blueprint
name (if any) will be used.
:param _anchor: If given, append this as ``#anchor`` to the URL.
:param _method: If given, generate the URL associated with this
method for the endpoint.
:param _scheme: If given, the URL will have this scheme if it
is external.
:param _external: If given, prefer the URL to be internal
(False) or require it to be external (True). External URLs
include the scheme and domain. When not in an active
request, URLs are external by default.
:param values: Values to use for the variable parts of the URL
rule. Unknown keys are appended as query string arguments,
like ``?a=b&c=d``.
.. versionadded:: 2.2
Moved from ``flask.url_for``, which calls this method.
req_ctx =
if req_ctx is not None:
url_adapter = req_ctx.url_adapter
blueprint_name = req_ctx.request.blueprint
# If the endpoint starts with "." and the request matches a
# blueprint, the endpoint is relative to the blueprint.
if endpoint[:1] == ".":
if blueprint_name is not None:
endpoint = f"{blueprint_name}{endpoint}"
endpoint = endpoint[1:]
# When in a request, generate a URL without scheme and
# domain by default, unless a scheme is given.
if _external is None:
_external = _scheme is not None
app_ctx =
# If called by helpers.url_for, an app context is active,
# use its url_adapter. Otherwise, app.url_for was called
# directly, build an adapter.
if app_ctx is not None:
url_adapter = app_ctx.url_adapter
url_adapter = self.create_url_adapter(None)
if url_adapter is None:
raise RuntimeError(
"Unable to build URLs outside an active request"
" without 'SERVER_NAME' configured. Also configure"
" needed."
# When outside a request, generate a URL with scheme and
# domain by default.
if _external is None:
_external = True
# It is an error to set _scheme when _external=False, in order
# to avoid accidental insecure URLs.
if _scheme is not None and not _external:
raise ValueError("When specifying '_scheme', '_external' must be True.")
self.inject_url_defaults(endpoint, values)
rv =
except BuildError as error:
_anchor=_anchor, _method=_method, _scheme=_scheme, _external=_external
return self.handle_url_build_error(error, endpoint, values)
if _anchor is not None:
rv = f"{rv}#{url_quote(_anchor)}"
return rv
def redirect(self, location: str, code: int = 302) -> BaseResponse:
"""Create a redirect response object.
This is called by :func:`flask.redirect`, and can be called
directly as well.
:param location: The URL to redirect to.
:param code: The status code for the redirect.
.. versionadded:: 2.2
Moved from ``flask.redirect``, which calls this method.
return _wz_redirect(location, code=code, Response=self.response_class)
def make_response(self, rv: ResponseReturnValue) -> Response:
"""Convert the return value from a view function to an instance of
:param rv: the return value from the view function. The view function
must return a response. Returning ``None``, or the view ending
without returning, is not allowed. The following types are allowed
for ``view_rv``:
A response object is created with the string encoded to UTF-8
as the body.
A response object is created with the bytes as the body.
A dictionary that will be jsonify'd before being returned.
Either ``(body, status, headers)``, ``(body, status)``, or
``(body, headers)``, where ``body`` is any of the other types
allowed here, ``status`` is a string or an integer, and
``headers`` is a dictionary or a list of ``(key, value)``
tuples. If ``body`` is a :attr:`response_class` instance,
``status`` overwrites the exiting value and ``headers`` are
The object is returned unchanged.
other :class:`~werkzeug.wrappers.Response` class
The object is coerced to :attr:`response_class`.
The function is called as a WSGI application. The result is
used to create a response object.
.. versionchanged:: 0.9
Previously a tuple was interpreted as the arguments for the
response object.
status = headers = None
# unpack tuple returns
if isinstance(rv, tuple):
len_rv = len(rv)
# a 3-tuple is unpacked directly
if len_rv == 3:
rv, status, headers = rv # type: ignore[misc]
# decide if a 2-tuple has status or headers
elif len_rv == 2:
if isinstance(rv[1], (Headers, dict, tuple, list)):
rv, headers = rv
rv, status = rv # type: ignore[misc]
# other sized tuples are not allowed
raise TypeError(
"The view function did not return a valid response tuple."
" The tuple must have the form (body, status, headers),"
" (body, status), or (body, headers)."
# the body must not be None
if rv is None:
raise TypeError(
f"The view function for {request.endpoint!r} did not"
" return a valid response. The function either returned"
" None or ended without a return statement."
# make sure the body is an instance of the response class
if not isinstance(rv, self.response_class):
if isinstance(rv, (str, bytes, bytearray)):
# let the response class set the status and headers instead of
# waiting to do it manually, so that the class can handle any
# special logic
rv = self.response_class(
headers=headers, # type: ignore[arg-type]
status = headers = None
elif isinstance(rv, dict):
rv = jsonify(rv)
elif isinstance(rv, BaseResponse) or callable(rv):
# evaluate a WSGI callable, or coerce a different response
# class to the correct type
rv = self.response_class.force_type(rv, request.environ) # type: ignore # noqa: B950
except TypeError as e:
raise TypeError(
f"{e}\nThe view function did not return a valid"
" response. The return type must be a string,"
" dict, tuple, Response instance, or WSGI"
f" callable, but it was a {type(rv).__name__}."
).with_traceback(sys.exc_info()[2]) from None
raise TypeError(
"The view function did not return a valid"
" response. The return type must be a string,"
" dict, tuple, Response instance, or WSGI"
f" callable, but it was a {type(rv).__name__}."
rv = t.cast(Response, rv)
# prefer the status if it was provided
if status is not None:
if isinstance(status, (str, bytes, bytearray)):
rv.status = status
rv.status_code = status
# extend existing headers with provided headers
if headers:
rv.headers.update(headers) # type: ignore[arg-type]
return rv
def create_url_adapter(
self, request: t.Optional[Request]
) -> t.Optional[MapAdapter]:
"""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.
.. versionadded:: 0.6
.. versionchanged:: 0.9
This can now also be called without a request object when the
URL adapter is created for the application context.
.. versionchanged:: 1.0
:data:`SERVER_NAME` no longer implicitly enables subdomain
matching. Use :attr:`subdomain_matching` instead.
if request is not None:
# If subdomain matching is disabled (the default), use the
# default subdomain in all cases. This should be the default
# in Werkzeug but it currently does not have that feature.
if not self.subdomain_matching:
subdomain = self.url_map.default_subdomain or None
subdomain = None
return self.url_map.bind_to_environ(
# We need at the very least the server name to be set for this
# to work.
if self.config["SERVER_NAME"] is not None:
return self.url_map.bind(
return None
def inject_url_defaults(self, endpoint: str, values: dict) -> None:
"""Injects the URL defaults for the given endpoint directly into
the values dictionary passed. This is used internally and
automatically called on URL building.
.. versionadded:: 0.7
names: t.Iterable[t.Optional[str]] = (None,)
# url_for may be called outside a request context, parse the
# passed endpoint instead of using request.blueprints.
if "." in endpoint:
names = chain(
names, reversed(_split_blueprint_path(endpoint.rpartition(".")[0]))
for name in names:
if name in self.url_default_functions:
for func in self.url_default_functions[name]:
func(endpoint, values)
def handle_url_build_error(
self, error: BuildError, endpoint: str, values: t.Dict[str, t.Any]
) -> str:
"""Called by :meth:`.url_for` if a
:exc:`~werkzeug.routing.BuildError` was raised. If this returns
a value, it will be returned by ``url_for``, otherwise the error
will be re-raised.
Each function in :attr:`url_build_error_handlers` is called with
``error``, ``endpoint`` and ``values``. If a function returns
``None`` or raises a ``BuildError``, it is skipped. Otherwise,
its return value is returned by ``url_for``.
:param error: The active ``BuildError`` being handled.
:param endpoint: The endpoint being built.
:param values: The keyword arguments passed to ``url_for``.
for handler in self.url_build_error_handlers:
rv = handler(error, endpoint, values)
except BuildError as e:
# make error available outside except block
error = e
if rv is not None:
return rv
# Re-raise if called with an active exception, otherwise raise
# the passed in exception.
if error is sys.exc_info()[1]:
raise error
def preprocess_request(self) -> t.Optional[ResponseReturnValue]:
"""Called before the request is dispatched. Calls
:attr:`url_value_preprocessors` registered with the app and the
current blueprint (if any). Then calls :attr:`before_request_funcs`
registered with the app and the blueprint.
If any :meth:`before_request` handler returns a non-None value, the
value is handled as if it was the return value from the view, and
further request handling is stopped.
names = (None, *reversed(request.blueprints))
for name in names:
if name in self.url_value_preprocessors:
for url_func in self.url_value_preprocessors[name]:
url_func(request.endpoint, request.view_args)
for name in names:
if name in self.before_request_funcs:
for before_func in self.before_request_funcs[name]:
rv = self.ensure_sync(before_func)()
if rv is not None:
return rv
return None
def process_response(self, response: 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 :meth:`after_request` decorated functions.
.. versionchanged:: 0.5
As of Flask 0.5 the functions registered for after request
execution are called in reverse order of registration.
:param response: a :attr:`response_class` object.
:return: a new response object or the same, has to be an
instance of :attr:`response_class`.
ctx =
for func in ctx._after_request_functions:
response = self.ensure_sync(func)(response)
for name in chain(request.blueprints, (None,)):
if name in self.after_request_funcs:
for func in reversed(self.after_request_funcs[name]):
response = self.ensure_sync(func)(response)
if not self.session_interface.is_null_session(ctx.session):
self.session_interface.save_session(self, ctx.session, response)
return response
def do_teardown_request(
self, exc: t.Optional[BaseException] = _sentinel # type: ignore
) -> None:
"""Called after the request is dispatched and the response is
returned, right before the request context is popped.
This calls all functions decorated with
:meth:`teardown_request`, and :meth:`Blueprint.teardown_request`
if a blueprint handled the request. Finally, the
:data:`request_tearing_down` signal is sent.
This is called by
:meth:`RequestContext.pop() <flask.ctx.RequestContext.pop>`,
which may be delayed during testing to maintain access to
:param exc: An unhandled exception raised while dispatching the
request. Detected from the current exception information if
not passed. Passed to each teardown function.
.. versionchanged:: 0.9
Added the ``exc`` argument.
if exc is _sentinel:
exc = sys.exc_info()[1]
for name in chain(request.blueprints, (None,)):
if name in self.teardown_request_funcs:
for func in reversed(self.teardown_request_funcs[name]):
request_tearing_down.send(self, exc=exc)
def do_teardown_appcontext(
self, exc: t.Optional[BaseException] = _sentinel # type: ignore
) -> None:
"""Called right before the application context is popped.
When handling a request, the application context is popped
after the request context. See :meth:`do_teardown_request`.
This calls all functions decorated with
:meth:`teardown_appcontext`. Then the
:data:`appcontext_tearing_down` signal is sent.
This is called by
:meth:`AppContext.pop() <flask.ctx.AppContext.pop>`.
.. versionadded:: 0.9
if exc is _sentinel:
exc = sys.exc_info()[1]
for func in reversed(self.teardown_appcontext_funcs):
appcontext_tearing_down.send(self, exc=exc)
def app_context(self) -> AppContext:
"""Create an :class:`~flask.ctx.AppContext`. Use as a ``with``
block to push the context, which will make :data:`current_app`
point at this application.
An application context is automatically pushed by
:meth:`RequestContext.push() <flask.ctx.RequestContext.push>`
when handling a request, and when running a CLI command. Use
this to manually create a context outside of these situations.
with app.app_context():
See :doc:`/appcontext`.
.. versionadded:: 0.9
return AppContext(self)
def request_context(self, environ: dict) -> RequestContext:
"""Create a :class:`~flask.ctx.RequestContext` representing a
WSGI environment. Use a ``with`` block to push the context,
which will make :data:`request` point at this request.
See :doc:`/reqcontext`.
Typically you should not call this from your own code. A request
context is automatically pushed by the :meth:`wsgi_app` when
handling a request. Use :meth:`test_request_context` to create
an environment and context instead of this method.
:param environ: a WSGI environment
return RequestContext(self, environ)
def test_request_context(self, *args: t.Any, **kwargs: t.Any) -> RequestContext:
"""Create a :class:`~flask.ctx.RequestContext` for a WSGI
environment created from the given values. This is mostly useful
during testing, where you may want to run a function that uses
request data without dispatching a full request.
See :doc:`/reqcontext`.
Use a ``with`` block to push the context, which will make
:data:`request` point at the request for the created
environment. ::
with test_request_context(...):
When using the shell, it may be easier to push and pop the
context manually to avoid indentation. ::
ctx = app.test_request_context(...)
Takes the same arguments as Werkzeug's
:class:`~werkzeug.test.EnvironBuilder`, with some defaults from
the application. See the linked Werkzeug docs for most of the
available arguments. Flask-specific behavior is listed here.
:param path: URL path being requested.
:param base_url: Base URL where the app is being served, which
``path`` is relative to. If not given, built from
:data:`PREFERRED_URL_SCHEME`, ``subdomain``,
:data:`SERVER_NAME`, and :data:`APPLICATION_ROOT`.
:param subdomain: Subdomain name to append to
:param url_scheme: Scheme to use instead of
:param data: The request body, either as a string or a dict of
form keys and values.
:param json: If given, this is serialized as JSON and passed as
``data``. Also defaults ``content_type`` to
:param args: other positional arguments passed to
:param kwargs: other keyword arguments passed to
from .testing import EnvironBuilder
builder = EnvironBuilder(self, *args, **kwargs)
return self.request_context(builder.get_environ())
def wsgi_app(self, environ: dict, start_response: t.Callable) -> t.Any:
"""The actual WSGI application. This is not implemented in
:meth:`__call__` so that middlewares can be applied without
losing a reference to the app object. 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.
.. versionchanged:: 0.7
Teardown events for the request and app contexts are called
even if an unhandled error occurs. Other events may not be
called depending on when an error occurs during dispatch.
See :ref:`callbacks-and-errors`.
:param environ: A WSGI environment.
:param start_response: A callable accepting a status code,
a list of headers, and an optional exception context to
start the response.
ctx = self.request_context(environ)
error: t.Optional[BaseException] = None
response = self.full_dispatch_request()
except Exception as e:
error = e
response = self.handle_exception(e)
except: # noqa: B001
error = sys.exc_info()[1]
return response(environ, start_response)
if self.should_ignore_error(error):
error = None
def __call__(self, environ: dict, start_response: t.Callable) -> t.Any:
"""The WSGI server calls the Flask application object as the
WSGI application. This calls :meth:`wsgi_app`, which can be
wrapped to apply middleware.
return self.wsgi_app(environ, start_response)