Utilities¶
Various utility functions shipped with Werkzeug.
General Helpers¶
- class werkzeug.utils.cached_property(fget, name=None, doc=None)¶
A
property()
that is only evaluated once. Subsequent access returns the cached value. Setting the property sets the cached value. Deleting the property clears the cached value, accessing it again will evaluate it again.class Example: @cached_property def value(self): # calculate something important here return 42 e = Example() e.value # evaluates e.value # uses cache e.value = 16 # sets cache del e.value # clears cache
If the class defines
__slots__
, it must add_cache_{name}
as a slot. Alternatively, it can add__dict__
, but that’s usually not desirable.Changelog
Changed in version 2.1: Works with
__slots__
.Changed in version 2.0:
del obj.name
clears the cached value.
- class werkzeug.utils.environ_property(name, default=None, load_func=None, dump_func=None, read_only=None, doc=None)¶
Maps request attributes to environment variables. This works not only for the Werkzeug request object, but also any other class with an environ attribute:
>>> class Test(object): ... environ = {'key': 'value'} ... test = environ_property('key') >>> var = Test() >>> var.test 'value'
If you pass it a second value it’s used as default if the key does not exist, the third one can be a converter that takes a value and converts it. If it raises
ValueError
orTypeError
the default value is used. If no default value is provided None is used.Per default the property is read only. You have to explicitly enable it by passing
read_only=False
to the constructor.
- class werkzeug.utils.header_property(name, default=None, load_func=None, dump_func=None, read_only=None, doc=None)¶
Like environ_property but for headers.
- werkzeug.utils.redirect(location, code=302, Response=None)¶
Returns a response object (a WSGI application) that, if called, redirects the client to the target location. Supported codes are 301, 302, 303, 305, 307, and 308. 300 is not supported because it’s not a real redirect and 304 because it’s the answer for a request with a request with defined If-Modified-Since headers.
Changelog
New in version 0.10: The class used for the Response object can now be passed in.
New in version 0.6: The location can now be a unicode string that is encoded using the
iri_to_uri()
function.- Parameters:
location (str) – the location the response should redirect to.
code (int) – the redirect status code. defaults to 302.
Response (class) – a Response class to use when instantiating a response. The default is
werkzeug.wrappers.Response
if unspecified.
- Return type:
- werkzeug.utils.append_slash_redirect(environ, code=308)¶
Redirect to the current URL with a slash appended.
If the current URL is
/user/42
, the redirect URL will be42/
. When joined to the current URL during response processing or by the browser, this will produce/user/42/
.The behavior is undefined if the path ends with a slash already. If called unconditionally on a URL, it may produce a redirect loop.
- Parameters:
environ (WSGIEnvironment) – Use the path and query from this WSGI environment to produce the redirect URL.
code (int) – the status code for the redirect.
- Return type:
Changelog
Changed in version 2.1: Produce a relative URL that only modifies the last segment. Relevant when the current path has multiple segments.
Changed in version 2.1: The default status code is 308 instead of 301. This preserves the request method and body.
- werkzeug.utils.send_file(path_or_file, environ, mimetype=None, as_attachment=False, download_name=None, conditional=True, etag=True, last_modified=None, max_age=None, use_x_sendfile=False, response_class=None, _root_path=None)¶
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
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
send_from_directory()
to safely serve user-provided paths.If the WSGI server sets a
file_wrapper
inenviron
, it is used, otherwise Werkzeug’s built-in wrapper is used. Alternatively, if the HTTP server supportsX-Sendfile
,use_x_sendfile=True
will tell the server to send the given path, which is much more efficient than reading it in Python.- Parameters:
path_or_file (os.PathLike | str | t.IO[bytes]) – 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.
environ (WSGIEnvironment) – The WSGI environ for the current request.
mimetype (str | None) – The MIME type to send for the file. If not provided, it will try to detect it from the file name.
as_attachment (bool) – Indicate to a browser that it should offer to save the file instead of displaying it.
download_name (str | None) – The default name browsers will use when saving the file. Defaults to the passed file name.
conditional (bool) – Enable conditional and range responses based on request headers. Requires passing a file path and
environ
.etag (bool | str) – Calculate an ETag for the file, which requires passing a file path. Can also be a string to use instead.
last_modified (datetime | int | float | None) – The last modified time to send for the file, in seconds. If not provided, it will try to detect it from the file path.
max_age (None | (int | t.Callable[[str | None], int | None])) – How long the client should cache the file, in seconds. If set,
Cache-Control
will bepublic
, otherwise it will beno-cache
to prefer conditional caching.use_x_sendfile (bool) – Set the
X-Sendfile
header to let the server to efficiently send the file. Requires support from the HTTP server. Requires passing a file path.response_class (type[Response] | None) – Build the response using this class. Defaults to
Response
._root_path (os.PathLike | str | None) – Do not use. For internal use only. Use
send_from_directory()
to safely send files under a path.
- Return type:
Changelog
Changed in version 2.0.2:
send_file
only sets a detectedContent-Encoding
ifas_attachment
is disabled.New in version 2.0: Adapted from Flask’s implementation.
Changed in version 2.0:
download_name
replaces Flask’sattachment_filename
parameter. Ifas_attachment=False
, it is passed withContent-Disposition: inline
instead.Changed in version 2.0:
max_age
replaces Flask’scache_timeout
parameter.conditional
is enabled andmax_age
is not set by default.Changed in version 2.0:
etag
replaces Flask’sadd_etags
parameter. It can be a string to use instead of generating one.Changed in version 2.0: If an encoding is returned when guessing
mimetype
fromdownload_name
, set theContent-Encoding
header.
- werkzeug.utils.send_from_directory(directory, path, environ, **kwargs)¶
Send a file from within a directory using
send_file()
.This is a secure way to serve files from a folder, such as static files or uploads. Uses
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, returns a 404
NotFound
error.- Parameters:
directory (os.PathLike | str) – The directory that
path
must be located under. This must not be a value provided by the client, otherwise it becomes insecure.path (os.PathLike | str) – The path to the file to send, relative to
directory
. This is the part of the path provided by the client, which is checked for security.environ (WSGIEnvironment) – The WSGI environ for the current request.
kwargs (t.Any) – Arguments to pass to
send_file()
.
- Return type:
Changelog
New in version 2.0: Adapted from Flask’s implementation.
- werkzeug.utils.import_string(import_name, silent=False)¶
Imports an object based on a string. This is useful if you want to use import paths as endpoints or something similar. An import path can be specified either in dotted notation (
xml.sax.saxutils.escape
) or with a colon as object delimiter (xml.sax.saxutils:escape
).If silent is True the return value will be None if the import fails.
- werkzeug.utils.find_modules(import_path, include_packages=False, recursive=False)¶
Finds all the modules below a package. This can be useful to automatically import all views / controllers so that their metaclasses / function decorators have a chance to register themselves on the application.
Packages are not returned unless include_packages is True. This can also recursively list modules but in that case it will import all the packages to get the correct load path of that module.
- werkzeug.utils.secure_filename(filename)¶
Pass it a filename and it will return a secure version of it. This filename can then safely be stored on a regular file system and passed to
os.path.join()
. The filename returned is an ASCII only string for maximum portability.On windows systems the function also makes sure that the file is not named after one of the special device files.
>>> secure_filename("My cool movie.mov") 'My_cool_movie.mov' >>> secure_filename("../../../etc/passwd") 'etc_passwd' >>> secure_filename('i contain cool \xfcml\xe4uts.txt') 'i_contain_cool_umlauts.txt'
The function might return an empty filename. It’s your responsibility to ensure that the filename is unique and that you abort or generate a random filename if the function returned an empty one.
Changelog
New in version 0.5.
URL Helpers¶
Please refer to URL Helpers.
User Agent API¶
- class werkzeug.user_agent.UserAgent(string)¶
Represents a parsed user agent header value.
The default implementation does no parsing, only the
string
attribute is set. A subclass may parse the string to set the common attributes or expose other information. Setwerkzeug.wrappers.Request.user_agent_class
to use a subclass.- Parameters:
string (str) – The header value to parse.
Changelog
New in version 2.0: This replaces the previous
useragents
module, but does not provide a built-in parser.
Security Helpers¶
- werkzeug.security.generate_password_hash(password, method='scrypt', salt_length=16)¶
Securely hash a password for storage. A password can be compared to a stored hash using
check_password_hash()
.The following methods are supported:
scrypt
, the default. The parameters aren
,r
, andp
, the default isscrypt:32768:8:1
. Seehashlib.scrypt()
.pbkdf2
, less secure. The parameters arehash_method
anditerations
, the default ispbkdf2:sha256:600000
. Seehashlib.pbkdf2_hmac()
.
Default parameters may be updated to reflect current guidelines, and methods may be deprecated and removed if they are no longer considered secure. To migrate old hashes, you may generate a new hash when checking an old hash, or you may contact users with a link to reset their password.
- Parameters:
- Return type:
Changelog
Changed in version 2.3: Scrypt support was added.
Changed in version 2.3: The default iterations for pbkdf2 was increased to 600,000.
Changed in version 2.3: All plain hashes are deprecated and will not be supported in Werkzeug 3.0.
- werkzeug.security.check_password_hash(pwhash, password)¶
Securely check that the given stored password hash, previously generated using
generate_password_hash()
, matches the given password.Methods may be deprecated and removed if they are no longer considered secure. To migrate old hashes, you may generate a new hash when checking an old hash, or you may contact users with a link to reset their password.
- Parameters:
- Return type:
Changelog
Changed in version 2.3: All plain hashes are deprecated and will not be supported in Werkzeug 3.0.
- werkzeug.security.safe_join(directory, *pathnames)¶
Safely join zero or more untrusted path components to a base directory to avoid escaping the base directory.
Logging¶
Werkzeug uses standard Python logging
. The logger is named
"werkzeug"
.
import logging
logger = logging.getLogger("werkzeug")
If the logger level is not set, it will be set to INFO
on first use. If there is no handler for that level, a
StreamHandler
is added.