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# -*- coding: utf-8 -*-
A microframework based on Werkzeug. It's extensively documented
and follows best practice patterns.
:copyright: (c) 2010 by Armin Ronacher.
:license: BSD, see LICENSE for more details.
from __future__ import with_statement
import os
import sys
import mimetypes
from datetime import datetime, timedelta
from itertools import chain
from threading import Lock
from jinja2 import Environment, PackageLoader, FileSystemLoader
from werkzeug import Request as RequestBase, Response as ResponseBase, \
LocalStack, LocalProxy, create_environ, SharedDataMiddleware, \
ImmutableDict, cached_property, wrap_file, Headers, \
from werkzeug.routing import Map, Rule
from werkzeug.exceptions import HTTPException, InternalServerError
from werkzeug.contrib.securecookie import SecureCookie
# try to load the best simplejson implementation available. If JSON
# is not installed, we add a failing class.
json_available = True
import simplejson as json
except ImportError:
import json
except ImportError:
json_available = False
# utilities we import from Werkzeug and Jinja2 that are unused
# in the module but are exported as public interface.
from werkzeug import abort, redirect
from jinja2 import Markup, escape
# use pkg_resource if that works, otherwise fall back to cwd. The
# current working directory is generally not reliable with the notable
# exception of google appengine.
import pkg_resources
except (ImportError, AttributeError):
pkg_resources = None
# a lock used for logger initialization
_logger_lock = Lock()
class Request(RequestBase):
"""The request object used by default in flask. Remembers the
matched endpoint and view arguments.
It is what ends up as :class:`~flask.request`. If you want to replace
the request object used you can subclass this and set
:attr:`~flask.Flask.request_class` to your subclass.
endpoint = view_args = routing_exception = None
def module(self):
"""The name of the current module"""
if self.endpoint and '.' in self.endpoint:
return self.endpoint.rsplit('.', 1)[0]
def json(self):
"""If the mimetype is `application/json` this will contain the
parsed JSON data.
if __debug__:
if self.mimetype == 'application/json':
return json.loads(
class Response(ResponseBase):
"""The response object that is used by default in flask. Works like the
response object from Werkzeug but is set to have a HTML mimetype by
default. Quite often you don't have to create this object yourself because
:meth:`~flask.Flask.make_response` will take care of that for you.
If you want to replace the response object used you can subclass this and
set :attr:`~flask.Flask.response_class` to your subclass.
default_mimetype = 'text/html'
class _RequestGlobals(object):
class Session(SecureCookie):
"""Expands the session with support for switching between permanent
and non-permanent sessions.
def _get_permanent(self):
return self.get('_permanent', False)
def _set_permanent(self, value):
self['_permanent'] = bool(value)
permanent = property(_get_permanent, _set_permanent)
del _get_permanent, _set_permanent
class _NullSession(Session):
"""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.
def _fail(self, *args, **kwargs):
raise RuntimeError('the session is unavailable because no secret '
'key was set. Set the secret_key on the '
'application to something unique and secret')
__setitem__ = __delitem__ = clear = pop = popitem = \
update = setdefault = _fail
del _fail
class _RequestContext(object):
"""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.
def __init__(self, app, environ): = app
self.url_adapter = app.url_map.bind_to_environ(environ)
self.request = app.request_class(environ)
self.session = app.open_session(self.request)
if self.session is None:
self.session = _NullSession()
self.g = _RequestGlobals()
self.flashes = None
self.request.endpoint, self.request.view_args = \
except HTTPException, e:
self.request.routing_exception = e
def push(self):
"""Binds the request context."""
def pop(self):
"""Pops the request context."""
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, tb):
# do not pop the request stack if we are in debug mode and an
# exception happened. This will allow the debugger to still
# access the request object in the interactive shell. Furthermore
# the context can be force kept alive for the test client.
if not self.request.environ.get('flask._preserve_context') and \
(tb is None or not
def url_for(endpoint, **values):
"""Generates a URL to the given endpoint with the method provided.
The endpoint is relative to the active module if modules are in use.
Here some examples:
==================== ======================= =============================
Active Module Target Endpoint Target Function
==================== ======================= =============================
`None` ``'index'`` `index` of the application
`None` ``'.index'`` `index` of the application
``'admin'`` ``'index'`` `index` of the `admin` module
any ``'.index'`` `index` of the application
any ``'admin.index'`` `index` of the `admin` module
==================== ======================= =============================
Variable arguments that are unknown to the target endpoint are appended
to the generated URL as query arguments.
For more information, head over to the :ref:`Quickstart <url-building>`.
:param endpoint: the endpoint of the URL (name of the function)
:param values: the variable arguments of the URL rule
:param _external: if set to `True`, an absolute URL is generated.
ctx =
if '.' not in endpoint:
mod = ctx.request.module
if mod is not None:
endpoint = mod + '.' + endpoint
elif endpoint.startswith('.'):
endpoint = endpoint[1:]
external = values.pop('_external', False)
return, values, force_external=external)
def 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 `_foo.html` with the following contents:
.. sourcecode:: html+jinja
{% macro hello(name) %}Hello {{ name }}!{% endmacro %}
You can access this from Python code like this::
hello = get_template_attribute('_foo.html', 'hello')
return hello('World')
.. versionadded:: 0.2
:param template_name: the name of the template
:param attribute: the name of the variable of macro to acccess
return getattr(current_app.jinja_env.get_template(template_name).module,
def 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 :func:`get_flashed_messages`.
.. versionchanged: 0.3
`category` parameter added.
:param message: the message to be flashed.
:param 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.
session.setdefault('_flashes', []).append((category, message))
def get_flashed_messages(with_categories=False):
"""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.
Example usage:
.. sourcecode:: html+jinja
{% for category, msg in get_flashed_messages(with_categories=true) %}
<p class=flash-{{ category }}>{{ msg }}
{% endfor %}
.. versionchanged:: 0.3
`with_categories` parameter added.
:param with_categories: set to `True` to also receive categories.
flashes =
if flashes is None: = flashes = session.pop('_flashes', [])
if not with_categories:
return [x[1] for x in flashes]
return flashes
def jsonify(*args, **kwargs):
"""Creates a :class:`~flask.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 :class:`dict` constructor.
Example usage::
def get_current_user():
return jsonify(username=g.user.username,,
This will send a JSON response like this to the browser::
"username": "admin",
"email": "admin@localhost",
"id": 42
This requires Python 2.6 or an installed version of simplejson.
.. versionadded:: 0.2
if __debug__:
return current_app.response_class(json.dumps(dict(*args, **kwargs),
indent=None if request.is_xhr else 2), mimetype='application/json')
def send_file(filename_or_fp, mimetype=None, as_attachment=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 :attr:`~Flask.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 sent certain files as attachment (HTML for instance).
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('/'):
.. versionadded:: 0.2
:param filename_or_fp: the filename of the file to send. This is
relative to the :attr:`~Flask.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.
:param mimetype: the mimetype of the file if provided, otherwise
auto detection happens.
:param as_attachment: set to `True` if you want to send this file with
a ``Content-Disposition: attachment`` header.
:param attachment_filename: the filename for the attachment if it
differs from the file's filename.
if isinstance(filename_or_fp, basestring):
filename = filename_or_fp
file = None
file = filename_or_fp
filename = getattr(file, 'name', None)
if filename is not None:
filename = os.path.join(current_app.root_path, filename)
if mimetype is None and (filename or attachment_filename):
mimetype = mimetypes.guess_type(filename or attachment_filename)[0]
if mimetype is None:
mimetype = 'application/octet-stream'
headers = Headers()
if as_attachment:
if attachment_filename is None:
if filename is None:
raise TypeError('filename unavailable, required for '
'sending as attachment')
attachment_filename = os.path.basename(filename)
headers.add('Content-Disposition', 'attachment',
if current_app.use_x_sendfile and filename:
if file is not None:
headers['X-Sendfile'] = filename
data = None
if file is None:
file = open(filename, 'rb')
data = wrap_file(request.environ, file)
return Response(data, mimetype=mimetype, headers=headers,
def render_template(template_name, **context):
"""Renders a template from the template folder with the given
:param template_name: the name of the template to be rendered
:param context: the variables that should be available in the
context of the template.
return current_app.jinja_env.get_template(template_name).render(context)
def render_template_string(source, **context):
"""Renders a template from the given template source string
with the given context.
:param template_name: the sourcecode of the template to be
:param context: the variables that should be available in the
context of the template.
return current_app.jinja_env.from_string(source).render(context)
def _default_template_ctx_processor():
"""Default template context processor. Injects `request`,
`session` and `g`.
reqctx =
return dict(
def _assert_have_json():
"""Helper function that fails if JSON is unavailable."""
if not json_available:
raise RuntimeError('simplejson not installed')
def _get_package_path(name):
"""Returns the path to a package or cwd if that cannot be found."""
return os.path.abspath(os.path.dirname(sys.modules[name].__file__))
except (KeyError, AttributeError):
return os.getcwd()
# figure out if simplejson escapes slashes. This behaviour was changed
# from one version to another without reason.
if not json_available or '\\/' not in json.dumps('/'):
def _tojson_filter(*args, **kwargs):
if __debug__:
return json.dumps(*args, **kwargs).replace('/', '\\/')
_tojson_filter = json.dumps
class _PackageBoundObject(object):
def __init__(self, import_name):
#: The name of the package or module. Do not change this once
#: it was set by the constructor.
self.import_name = import_name
#: Where is the app root located?
self.root_path = _get_package_path(self.import_name)
def open_resource(self, resource):
"""Opens a resource from the application's resource folder. To see
how this works, consider the following folder structure::
If you want to open the `schema.sql` file you would do the
with app.open_resource('schema.sql') as f:
contents =
:param resource: the name of the resource. To access resources within
subfolders use forward slashes as separator.
if pkg_resources is None:
return open(os.path.join(self.root_path, resource), 'rb')
return pkg_resources.resource_stream(self.import_name, resource)
class _ModuleSetupState(object):
def __init__(self, app, url_prefix=None): = app
self.url_prefix = url_prefix
class Module(_PackageBoundObject):
"""Container object that enables pluggable applications. A module can
be used to organize larger applications. They represent blueprints that,
in combination with a :class:`Flask` object are used to create a large
A module is like an application bound to an `import_name`. Multiple
modules can share the same import names, but in that case a `name` has
to be provided to keep them apart. If different import names are used,
the rightmost part of the import name is used as name.
Here an example structure for a larger appliation::
The `myapplication/` can look like this::
from flask import Flask
from myapplication.views.admin import admin
from myapplication.views.frontend import frontend
app = Flask(__name__)
app.register_module(admin, url_prefix='/admin')
And here an example view module (`myapplication/views/`)::
from flask import Module
admin = Module(__name__)
def index():
def login():
For a gentle introduction into modules, checkout the
:ref:`working-with-modules` section.
def __init__(self, import_name, name=None, url_prefix=None):
if name is None:
assert '.' in import_name, 'name required if package name ' \
'does not point to a submodule'
name = import_name.rsplit('.', 1)[1]
_PackageBoundObject.__init__(self, import_name) = name
self.url_prefix = url_prefix
self._register_events = []
def route(self, rule, **options):
"""Like :meth:`Flask.route` but for a module. The endpoint for the
:func:`url_for` function is prefixed with the name of the module.
def decorator(f):
self.add_url_rule(rule, f.__name__, f, **options)
return f
return decorator
def add_url_rule(self, rule, endpoint, view_func=None, **options):
"""Like :meth:`Flask.add_url_rule` but for a module. The endpoint for
the :func:`url_for` function is prefixed with the name of the module.
def register_rule(state):
the_rule = rule
if state.url_prefix:
the_rule = state.url_prefix + rule, '%s.%s' % (, endpoint),
view_func, **options)
def before_request(self, f):
"""Like :meth:`Flask.before_request` but for a module. This function
is only executed before each request that is handled by a function of
that module.
self._record(lambda s:
.setdefault(, []).append(f))
return f
def before_app_request(self, f):
"""Like :meth:`Flask.before_request`. Such a function is executed
before each request, even if outside of a module.
self._record(lambda s:
.setdefault(None, []).append(f))
return f
def after_request(self, f):
"""Like :meth:`Flask.after_request` but for a module. This function
is only executed after each request that is handled by a function of
that module.
self._record(lambda s:
.setdefault(, []).append(f))
return f
def after_app_request(self, f):
"""Like :meth:`Flask.after_request` but for a module. Such a function
is executed after each request, even if outside of the module.
self._record(lambda s:
.setdefault(None, []).append(f))
return f
def context_processor(self, f):
"""Like :meth:`Flask.context_processor` but for a module. This
function is only executed for requests handled by a module.
self._record(lambda s:
.setdefault(, []).append(f))
return f
def app_context_processor(self, f):
"""Like :meth:`Flask.context_processor` but for a module. Such a
function is executed each request, even if outside of the module.
self._record(lambda s:
.setdefault(None, []).append(f))
return f
def app_errorhandler(self, code):
"""Like :meth:`Flask.errorhandler` but for a module. This
handler is used for all requests, even if outside of the module.
.. versionadded:: 0.4
def decorator(f):
self._record(lambda s:
return f
return decorator
def _record(self, func):
class ConfigAttribute(object):
"""Makes an attribute forward to the config"""
def __init__(self, name):
self.__name__ = name
def __get__(self, obj, type=None):
if obj is None:
return self
return obj.config[self.__name__]
def __set__(self, obj, value):
obj.config[self.__name__] = value
class Config(dict):
"""Works exactly like a dict but provides ways to fill it from files
or special dictionaries. There are two common patterns to populate the
Either you can fill the config from a config file::
Or alternatively you can define the configuration options in the
module that calls :meth:`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'
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::
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.
:param root_path: path to which files are read relative from. When the
config object is created by the application, this is
the application's :attr:`~flask.Flask.root_path`.
:param defaults: an optional dictionary of default values
def __init__(self, root_path, defaults=None):
dict.__init__(self, defaults or {})
self.root_path = root_path
def from_envvar(self, variable_name, silent=False):
"""Loads a configuration from an environment variable pointing to
a configuration file. This basically is just a shortcut with nicer
error messages for this line of code::
:param variable_name: name of the environment variable
:param silent: set to `True` if you want silent failing for missing
:return: bool. `True` if able to load config, `False` otherwise.
rv = os.environ.get(variable_name)
if not rv:
if silent:
return False
raise RuntimeError('The environment variable %r is not set '
'and as such configuration could not be '
'loaded. Set this variable and make it '
'point to a configuration file' %
return True
def from_pyfile(self, filename):
"""Updates the values in the config from a Python file. This function
behaves as if the file was imported as module with the
:meth:`from_object` function.
:param filename: the filename of the config. This can either be an
absolute filename or a filename relative to the
root path.
filename = os.path.join(self.root_path, filename)
d = type(sys)('config')
d.__file__ = filename
execfile(filename, d.__dict__)
def from_object(self, 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
after lowercasing. Example usage::
from yourapplication import default_config
You should not use this function to load the actual configuration but
rather configuration defaults. The actual config should be loaded
with :meth:`from_pyfile` and ideally from a location not within the
package because the package might be installed system wide.
:param obj: an import name or object
if isinstance(obj, basestring):
obj = import_string(obj)
for key in dir(obj):
if key.isupper():
self[key] = getattr(obj, key)
def __repr__(self):
return '<%s %s>' % (self.__class__.__name__, dict.__repr__(self))
class Flask(_PackageBoundObject):
"""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 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 of your package like this::
from flask import Flask
app = Flask(__name__)
#: 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
#: Path for the static files. If you don't want to use static files
#: you can set this value to `None` in which case no URL rule is added
#: and the development server will no longer serve any static files.
static_path = '/static'
#: 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 ocurrs 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 = ConfigAttribute('DEBUG')
#: The testing flask. 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.
#: 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
#: `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')
#: 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 name of the logger to use. By default the logger name is the
#: package name passed to the constructor.
#: .. versionadded:: 0.4
logger_name = ConfigAttribute('LOGGER_NAME')
#: 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.
#: .. versionadded:: 0.3
debug_log_format = (
'-' * 80 + '\n' +
'%(levelname)s in %(module)s, %(pathname)s:%(lineno)d]:\n' +
'%(message)s\n' +
'-' * 80
#: Options that are passed directly to the Jinja2 environment.
jinja_options = ImmutableDict(
extensions=['jinja2.ext.autoescape', 'jinja2.ext.with_']
#: Default configuration parameters.
default_config = ImmutableDict({
'DEBUG': False,
'TESTING': False,
'PERMANENT_SESSION_LIFETIME': timedelta(days=31),
def __init__(self, import_name):
_PackageBoundObject.__init__(self, import_name)
#: 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 = Config(self.root_path, self.default_config)
#: Prepare the deferred setup of the logger.
self._logger = None
self.logger_name = self.import_name
#: 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 :meth:`route` decorator.
self.view_functions = {}
#: A dictionary of all registered error handlers. The key is
#: be the error code as integer, the value the function that
#: should handle that error.
#: To register a error handler, use the :meth:`errorhandler`
#: decorator.
self.error_handlers = {}
#: 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 module 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 :meth:`before_request` decorator.
self.before_request_funcs = {}
#: A dictionary with lists of functions that should be called after
#: each request. The key of the dictionary is the name of the module
#: 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
#: :meth:`before_request` decorator.
self.after_request_funcs = {}
#: A dictionary with list of functions that are called without argument
#: to populate the template context. They key of the dictionary is the
#: name of the module 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
#: :meth:`context_processor` decorator.
self.template_context_processors = {
None: [_default_template_ctx_processor]
#: 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 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
self.url_map = Map()
if self.static_path is not None:
self.add_url_rule(self.static_path + '/<filename>',
build_only=True, endpoint='static')
if pkg_resources is not None:
target = (self.import_name, 'static')
target = os.path.join(self.root_path, 'static')
self.wsgi_app = SharedDataMiddleware(self.wsgi_app, {
self.static_path: target
#: The Jinja2 environment. It is created from the
#: :attr:`jinja_options` and the loader that is returned
#: by the :meth:`create_jinja_loader` function.
self.jinja_env = Environment(loader=self.create_jinja_loader(),
self.jinja_env.filters['tojson'] = _tojson_filter
def logger(self):
"""A :class:`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 ocurred (%d apples)', 42)
app.logger.error('An error occoured')
.. versionadded:: 0.3
if self._logger and == self.logger_name:
return self._logger
with _logger_lock:
if self._logger and == self.logger_name:
return self._logger
from logging import getLogger, StreamHandler, Formatter, DEBUG
class DebugHandler(StreamHandler):
def emit(x, record):
if self.debug:
StreamHandler.emit(x, record)
handler = DebugHandler()
logger = getLogger(self.logger_name)
self._logger = logger
return logger
def create_jinja_loader(self):
"""Creates the Jinja loader. By default just a package loader for
the configured package is returned that looks up templates in the
`templates` folder. To add other loaders it's possible to
override this method.
if pkg_resources is None:
return FileSystemLoader(os.path.join(self.root_path, 'templates'))
return PackageLoader(self.import_name)
def update_template_context(self, context):
"""Update the template context with some commonly used variables.
This injects request, session and g into the template context.
:param context: the context as a dictionary that is updated in place
to add extra variables.
funcs = self.template_context_processors[None]
mod =
if mod is not None and mod in self.template_context_processors:
funcs = chain(funcs, self.template_context_processors[mod])
for func in funcs:
def run(self, host='', port=5000, **options):
"""Runs the application on a local development server. If the
:attr:`debug` flag is set the server will automatically reload
for code changes and show a debugger in case an exception happened.
:param host: the hostname to listen on. set this to ``''``
to have the server available externally as well.
:param port: the port of the webserver
:param options: the options to be forwarded to the underlying
Werkzeug server. See :func:`werkzeug.run_simple`
for more information.
from werkzeug import run_simple
if 'debug' in options:
self.debug = options.pop('debug')
options.setdefault('use_reloader', self.debug)
options.setdefault('use_debugger', self.debug)
return run_simple(host, port, self, **options)
def test_client(self):
"""Creates a test client for this application. For information
about unit testing head over to :ref:`testing`.
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('/?foo=42')
assert request.args['foo'] == '42'
.. versionchanged:: 0.4
added support for `with` block usage for the client.
from werkzeug import Client
class FlaskClient(Client):
preserve_context = context_preserved = False
def open(self, *args, **kwargs):
if self.context_preserved:
self.context_preserved = False
kwargs.setdefault('environ_overrides', {}) \
['flask._preserve_context'] = self.preserve_context
old =
return, *args, **kwargs)
self.context_preserved = is not old
def __enter__(self):
self.preserve_context = True
return self
def __exit__(self, exc_type, exc_value, tb):
self.preserve_context = False
if self.context_preserved:
return FlaskClient(self, self.response_class, use_cookies=True)
def open_session(self, request):
"""Creates or opens a new session. Default implementation stores all
session data in a signed cookie. This requires that the
:attr:`secret_key` is set.
:param request: an instance of :attr:`request_class`.
key = self.secret_key
if key is not None:
return Session.load_cookie(request, self.session_cookie_name,
def save_session(self, session, response):
"""Saves the session if it needs updates. For the default
implementation, check :meth:`open_session`.
:param session: the session to be saved (a
:param response: an instance of :attr:`response_class`
expires = None
if session.permanent:
expires = datetime.utcnow() + self.permanent_session_lifetime
session.save_cookie(response, self.session_cookie_name,
expires=expires, httponly=True)
def register_module(self, 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
:class:`Module` class and will override the values of the module if
options.setdefault('url_prefix', module.url_prefix)
state = _ModuleSetupState(self, **options)
for func in module._register_events:
def add_url_rule(self, rule, endpoint=None, view_func=None, **options):
"""Connects a URL rule. Works exactly like the :meth:`route`
decorator. If a view_func is provided it will be registered with the
Basically this example::
def index():
Is equivalent to the following::
def index():
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
.. versionchanged:: 0.2
`view_func` parameter added.
:param rule: the URL rule as string
:param endpoint: the endpoint for the registered URL rule. Flask
itself assumes the name of the view function as
:param view_func: the function to call when serving a request to the
provided endpoint
:param options: the options to be forwarded to the underlying
:class:`~werkzeug.routing.Rule` object
if endpoint is None:
assert view_func is not None, 'expected view func if endpoint ' \
'is not provided.'
endpoint = view_func.__name__
options['endpoint'] = endpoint
options.setdefault('methods', ('GET',))
self.url_map.add(Rule(rule, **options))
if view_func is not None:
self.view_functions[endpoint] = view_func
def route(self, rule, **options):
"""A decorator that is used to register a view function for a
given URL rule. Example::
def index():
return 'Hello World'
Variables parts in the route can be specified with angular
brackets (``/user/<username>``). By default a variable part
in the URL accepts any string without a slash however a different
converter can be specified as well by using ``<converter:name>``.
Variable parts are passed to the view function as keyword
The following converters are possible:
=========== ===========================================
`int` accepts integers
`float` like `int` but for floating point values
`path` like the default but also accepts slashes
=========== ===========================================
Here some examples::
def index():
def show_user(username):
def show_post(post_id):
An important detail to keep in mind is how Flask deals with trailing
slashes. The idea is to keep each URL unique so the following rules
1. If a rule ends with a slash and is requested without a slash
by the user, the user is automatically redirected to the same
page with a trailing slash attached.
2. If a rule does not end with a trailing slash and the user request
the page with a trailing slash, a 404 not found is raised.
This is consistent with how web servers deal with static files. This
also makes it possible to use relative link targets safely.
The :meth:`route` decorator accepts a couple of other arguments
as well:
:param rule: the URL rule as string
:param methods: a list of methods this rule should be limited
to (``GET``, ``POST`` etc.). By default a rule
just listens for ``GET`` (and implicitly ``HEAD``).
:param subdomain: specifies the rule for the subdoain in case
subdomain matching is in use.
:param strict_slashes: can be used to disable the strict slashes
setting for this rule. See above.
:param options: other options to be forwarded to the underlying
:class:`~werkzeug.routing.Rule` object.
def decorator(f):
self.add_url_rule(rule, None, f, **options)
return f
return decorator
def errorhandler(self, code):
"""A decorator that is used to register a function give a given
error code. Example::
def page_not_found(error):
return 'This page does not exist', 404
You can also register a function as error handler without using
the :meth:`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_handlers[404] = page_not_found
:param code: the code as integer for the handler
def decorator(f):
self.error_handlers[code] = f
return f
return decorator
def template_filter(self, name=None):
"""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):
self.jinja_env.filters[name or f.__name__] = f
return f
return decorator
def before_request(self, f):
"""Registers a function to run before each request."""
self.before_request_funcs.setdefault(None, []).append(f)
return f
def after_request(self, f):
"""Register a function to be run after each request."""
self.after_request_funcs.setdefault(None, []).append(f)
return f
def context_processor(self, f):
"""Registers a template context processor function."""
return f
def handle_http_exception(self, e):
"""Handles an HTTP exception. By default this will invoke the
registered error handlers and fall back to returning the
exception as response.
.. versionadded: 0.3
handler = self.error_handlers.get(e.code)
if handler is None:
return e
return handler(e)
def handle_exception(self, e):
"""Default exception handling that kicks in when an exception
occours that is not catched. 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.
.. versionadded: 0.3
handler = self.error_handlers.get(500)
if self.debug:
self.logger.exception('Exception on %s [%s]' % (
if handler is None:
return InternalServerError()
return handler(e)
def dispatch_request(self):
"""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`.
req =
if req.routing_exception is not None:
raise req.routing_exception
return self.view_functions[req.endpoint](**req.view_args)
except HTTPException, e:
return self.handle_http_exception(e)
def make_response(self, rv):
"""Converts the return value from a view function to a real
response object that is an instance of :attr:`response_class`.
The following types are allowed for `rv`:
.. tabularcolumns:: |p{3.5cm}|p{9.5cm}|
======================= ===========================================
:attr:`response_class` the object is returned unchanged
:class:`str` a response object is created with the
string as body
:class:`unicode` a response object is created with the
string encoded to utf-8 as body
:class:`tuple` the response object is created with the
contents of the tuple as arguments
a WSGI function the function is called as WSGI application
and buffered as response object
======================= ===========================================
:param rv: the return value from the view function
if rv is None:
raise ValueError('View function did not return a response')
if isinstance(rv, self.response_class):
return rv
if isinstance(rv, basestring):
return self.response_class(rv)
if isinstance(rv, tuple):
return self.response_class(*rv)
return self.response_class.force_type(rv, request.environ)
def preprocess_request(self):
"""Called before the actual request dispatching and will
call every as :meth:`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.
funcs = self.before_request_funcs.get(None, ())
mod = request.module
if mod and mod in self.before_request_funcs:
funcs = chain(funcs, self.before_request_funcs[mod])
for func in funcs:
rv = func()
if rv is not None:
return rv
def process_response(self, 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.
: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 =
mod = ctx.request.module
if not isinstance(ctx.session, _NullSession):
self.save_session(ctx.session, response)
funcs = ()
if mod and mod in self.after_request_funcs:
funcs = chain(funcs, self.after_request_funcs[mod])
if None in self.after_request_funcs:
funcs = chain(funcs, self.after_request_funcs[None])
for handler in funcs:
response = handler(response)
return response
def wsgi_app(self, 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.
.. versionchanged:: 0.4
The :meth:`after_request` functions are now called even if an
error handler took over request processing. This ensures that
even if an exception happens database have the chance to
properly close the connection.
: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
with self.request_context(environ):
rv = self.preprocess_request()
if rv is None:
rv = self.dispatch_request()
response = self.make_response(rv)
except Exception, e:
response = self.make_response(self.handle_exception(e))
response = self.process_response(response)
except Exception, e:
response = self.make_response(self.handle_exception(e))
return response(environ, start_response)
def request_context(self, environ):
"""Creates a request context 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):
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)
The big advantage of this approach is that you can use it without
the try/finally statement in a shell for interactive testing:
>>> ctx = app.test_request_context()
>>> ctx.bind()
>>> request.path
>>> ctx.unbind()
.. versionchanged:: 0.3
Added support for non-with statement usage and `with` statement
is now passed the ctx object.
:param environ: a WSGI environment
return _RequestContext(self, environ)
def test_request_context(self, *args, **kwargs):
"""Creates a WSGI environment from the given values (see
:func:`werkzeug.create_environ` for more information, this
function accepts the same arguments).
return self.request_context(create_environ(*args, **kwargs))
def __call__(self, environ, start_response):
"""Shortcut for :attr:`wsgi_app`."""
return self.wsgi_app(environ, start_response)
# context locals
_request_ctx_stack = LocalStack()
current_app = LocalProxy(lambda:
request = LocalProxy(lambda:
session = LocalProxy(lambda:
g = LocalProxy(lambda:
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