HTTP Utilities

Werkzeug provides a couple of functions to parse and generate HTTP headers that are useful when implementing WSGI middlewares or whenever you are operating on a lower level layer. All this functionality is also exposed from request and response objects.

Datetime Functions

These functions simplify working with times in an HTTP context. Werkzeug produces timezone-aware datetime objects in UTC. When passing datetime objects to Werkzeug, it assumes any naive datetime is in UTC.

When comparing datetime values from Werkzeug, your own datetime objects must also be timezone-aware, or you must make the values from Werkzeug naive.

  • dt = datetime.now(timezone.utc) gets the current time in UTC.
  • dt = datetime(..., tzinfo=timezone.utc) creates a time in UTC.
  • dt = dt.replace(tzinfo=timezone.utc) makes a naive object aware by assuming it’s in UTC.
  • dt = dt.replace(tzinfo=None) makes an aware object naive.


Header Parsing

The following functions can be used to parse incoming HTTP headers. Because Python does not provide data structures with the semantics required by RFC 2616, Werkzeug implements some custom data structures that are documented separately.


Header Utilities

The following utilities operate on HTTP headers well but do not parse them. They are useful if you’re dealing with conditional responses or if you want to proxy arbitrary requests but want to remove WSGI-unsupported hop-by-hop headers. Also there is a function to create HTTP header strings from the parsed data.


Cookies

Conditional Response Helpers

For conditional responses the following functions might be useful:


Constants

werkzeug.http.HTTP_STATUS_CODES
A dict of status code -> default status message pairs. This is used by the wrappers and other places where an integer status code is expanded to a string throughout Werkzeug.


Form Data Parsing

Werkzeug provides the form parsing functions separately from the request object so that you can access form data from a plain WSGI environment.

The following formats are currently supported by the form data parser:

  • application/x-www-form-urlencoded
  • multipart/form-data

Nested multipart is not currently supported (Werkzeug 0.9), but it isn’t used by any of the modern web browsers.

Usage example:

>>> from io import BytesIO
>>> from werkzeug.formparser import parse_form_data
>>> data = (
...     b'--foo\r\nContent-Disposition: form-data; name="test"\r\n'
...     b"\r\nHello World!\r\n--foo--"
... )
>>> environ = {
...     "wsgi.input": BytesIO(data),
...     "CONTENT_LENGTH": str(len(data)),
...     "CONTENT_TYPE": "multipart/form-data; boundary=foo",
...     "REQUEST_METHOD": "POST",
... }
>>> stream, form, files = parse_form_data(environ)
>>> stream.read()
b''
>>> form['test']
'Hello World!'
>>> not files
True

Normally the WSGI environment is provided by the WSGI gateway with the incoming data as part of it. If you want to generate such fake-WSGI environments for unittesting you might want to use the create_environ() function or the EnvironBuilder instead.