flask.helpers

Raise an :exc:`~werkzeug.exceptions.HTTPException` for the given status code. If :data:`~flask.current_app` is available, it will call its :attr:`~flask.Flask.aborter` object, otherwise it will use :func:`werkzeug.exceptions.abort`. :param code: The status code for the exception, which must be registered in ``app.aborter``. :param args: Passed to the exception. :param kwargs: Passed to the exception. .. versionadded:: 2.2 Calls ``current_app.aborter`` if available instead of always using Werkzeug's default ``abort``.

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.

Get whether debug mode should be enabled for the app, indicated by the :envvar:`FLASK_DEBUG` environment variable. The default is ``False``.

Get the environment the app is running in, indicated by the :envvar:`FLASK_ENV` environment variable. The default is ``'production'``. .. deprecated:: 2.2 Will be removed in Flask 2.3.

Pulls all flashed messages from the session and returns them. Further calls in the same request to the function will return the same messages. By default just the messages are returned, but when `with_categories` is set to ``True``, the return value will be a list of tuples in the form ``(category, message)`` instead. Filter the flashed messages to one or more categories by providing those categories in `category_filter`. This allows rendering categories in separate html blocks. The `with_categories` and `category_filter` arguments are distinct: * `with_categories` controls whether categories are returned with message text (``True`` gives a tuple, where ``False`` gives just the message text). * `category_filter` filters the messages down to only those matching the provided categories. See :doc:`/patterns/flashing` for examples. .. versionchanged:: 0.3 `with_categories` parameter added. .. versionchanged:: 0.9 `category_filter` parameter added. :param with_categories: set to ``True`` to also receive categories. :param category_filter: filter of categories to limit return values. Only categories in the list will be returned.

Get whether the user has disabled loading default dotenv files by setting :envvar:`FLASK_SKIP_DOTENV`. The default is ``True``, load the files. :param default: What to return if the env var isn't set.

Find the root path of a package, or the path that contains a module. If it cannot be found, returns the current working directory. Not to be confused with the value returned by :func:`find_package`. :meta private:

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 :file:`_cider.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('_cider.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 access

Determine if the given string is an IP address. :param value: value to check :type value: str :return: True if string is an IP address :rtype: bool

Sometimes it is necessary to set additional headers in a view. Because views do not have to return response objects but can return a value that is converted into a response object by Flask itself, it becomes tricky to add headers to it. This function can be called instead of using a return and you will get a response object which you can use to attach headers. If view looked like this and you want to add a new header:: def index(): return render_template('index.html', foo=42) You can now do something like this:: def index(): response = make_response(render_template('index.html', foo=42)) response.headers['X-Parachutes'] = 'parachutes are cool' return response This function accepts the very same arguments you can return from a view function. This for example creates a response with a 404 error code:: response = make_response(render_template('not_found.html'), 404) The other use case of this function is to force the return value of a view function into a response which is helpful with view decorators:: response = make_response(view_function()) response.headers['X-Parachutes'] = 'parachutes are cool' Internally this function does the following things: - if no arguments are passed, it creates a new response argument - if one argument is passed, :meth:`flask.Flask.make_response` is invoked with it. - if more than one argument is passed, the arguments are passed to the :meth:`flask.Flask.make_response` function as tuple. .. versionadded:: 0.6

Create a redirect response object. If :data:`~flask.current_app` is available, it will use its :meth:`~flask.Flask.redirect` method, otherwise it will use :func:`werkzeug.utils.redirect`. :param location: The URL to redirect to. :param code: The status code for the redirect. :param Response: The response class to use. Not used when ``current_app`` is active, which uses ``app.response_class``. .. versionadded:: 2.2 Calls ``current_app.redirect`` if available instead of always using Werkzeug's default ``redirect``.

Send the contents of a file to the client. The first argument can be a file path or a file-like object. Paths are preferred in most cases because Werkzeug can manage the file and get extra information from the path. Passing a file-like object requires that the file is opened in binary mode, and is mostly useful when building a file in memory with :class:`io.BytesIO`. Never pass file paths provided by a user. The path is assumed to be trusted, so a user could craft a path to access a file you didn't intend. Use :func:`send_from_directory` to safely serve user-requested paths from within a directory. If the WSGI server sets a ``file_wrapper`` in ``environ``, it is used, otherwise Werkzeug's built-in wrapper is used. Alternatively, if the HTTP server supports ``X-Sendfile``, configuring Flask with ``USE_X_SENDFILE = True`` will tell the server to send the given path, which is much more efficient than reading it in Python. :param path_or_file: The path to the file to send, relative to the current working directory if a relative path is given. Alternatively, a file-like object opened in binary mode. Make sure the file pointer is seeked to the start of the data. :param mimetype: The MIME type to send for the file. If not provided, it will try to detect it from the file name. :param as_attachment: Indicate to a browser that it should offer to save the file instead of displaying it. :param download_name: The default name browsers will use when saving the file. Defaults to the passed file name. :param conditional: Enable conditional and range responses based on request headers. Requires passing a file path and ``environ``. :param etag: Calculate an ETag for the file, which requires passing a file path. Can also be a string to use instead. :param last_modified: The last modified time to send for the file, in seconds. If not provided, it will try to detect it from the file path. :param max_age: How long the client should cache the file, in seconds. If set, ``Cache-Control`` will be ``public``, otherwise it will be ``no-cache`` to prefer conditional caching. .. versionchanged:: 2.0 ``download_name`` replaces the ``attachment_filename`` parameter. If ``as_attachment=False``, it is passed with ``Content-Disposition: inline`` instead. .. versionchanged:: 2.0 ``max_age`` replaces the ``cache_timeout`` parameter. ``conditional`` is enabled and ``max_age`` is not set by default. .. versionchanged:: 2.0 ``etag`` replaces the ``add_etags`` parameter. It can be a string to use instead of generating one. .. versionchanged:: 2.0 Passing a file-like object that inherits from :class:`~io.TextIOBase` will raise a :exc:`ValueError` rather than sending an empty file. .. versionadded:: 2.0 Moved the implementation to Werkzeug. This is now a wrapper to pass some Flask-specific arguments. .. versionchanged:: 1.1 ``filename`` may be a :class:`~os.PathLike` object. .. versionchanged:: 1.1 Passing a :class:`~io.BytesIO` object supports range requests. .. versionchanged:: 1.0.3 Filenames are encoded with ASCII instead of Latin-1 for broader compatibility with WSGI servers. .. versionchanged:: 1.0 UTF-8 filenames as specified in :rfc:`2231` are supported. .. versionchanged:: 0.12 The filename is no longer automatically inferred from file objects. If you want to use automatic MIME and etag support, pass a filename via ``filename_or_fp`` or ``attachment_filename``. .. versionchanged:: 0.12 ``attachment_filename`` is preferred over ``filename`` for MIME detection. .. versionchanged:: 0.9 ``cache_timeout`` defaults to :meth:`Flask.get_send_file_max_age`. .. versionchanged:: 0.7 MIME guessing and etag support for file-like objects was deprecated because it was unreliable. Pass a filename if you are able to, otherwise attach an etag yourself. .. versionchanged:: 0.5 The ``add_etags``, ``cache_timeout`` and ``conditional`` parameters were added. The default behavior is to add etags. .. versionadded:: 0.2

Send a file from within a directory using :func:`send_file`. .. code-block:: python @app.route("/uploads/<path:name>") def download_file(name): return send_from_directory( app.config['UPLOAD_FOLDER'], name, as_attachment=True ) This is a secure way to serve files from a folder, such as static files or uploads. Uses :func:`~werkzeug.security.safe_join` to ensure the path coming from the client is not maliciously crafted to point outside the specified directory. If the final path does not point to an existing regular file, raises a 404 :exc:`~werkzeug.exceptions.NotFound` error. :param directory: The directory that ``path`` must be located under, relative to the current application's root path. :param path: The path to the file to send, relative to ``directory``. :param kwargs: Arguments to pass to :func:`send_file`. .. versionchanged:: 2.0 ``path`` replaces the ``filename`` parameter. .. versionadded:: 2.0 Moved the implementation to Werkzeug. This is now a wrapper to pass some Flask-specific arguments. .. versionadded:: 0.5

Request contexts disappear when the response is started on the server. This is done for efficiency reasons and to make it less likely to encounter memory leaks with badly written WSGI middlewares. The downside is that if you are using streamed responses, the generator cannot access request bound information any more. This function however can help you keep the context around for longer:: from flask import stream_with_context, request, Response @app.route('/stream') def streamed_response(): @stream_with_context def generate(): yield 'Hello ' yield request.args['name'] yield '!' return Response(generate()) Alternatively it can also be used around a specific generator:: from flask import stream_with_context, request, Response @app.route('/stream') def streamed_response(): def generate(): yield 'Hello ' yield request.args['name'] yield '!' return Response(stream_with_context(generate())) .. versionadded:: 0.9

Generate a URL to the given endpoint with the given values. This requires an active request or application context, and calls :meth:`current_app.url_for() <flask.Flask.url_for>`. See that method for full documentation. :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``. .. versionchanged:: 2.2 Calls ``current_app.url_for``, allowing an app to override the behavior. .. versionchanged:: 0.10 The ``_scheme`` parameter was added. .. versionchanged:: 0.9 The ``_anchor`` and ``_method`` parameters were added. .. versionchanged:: 0.9 Calls ``app.handle_url_build_error`` on build errors.