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.
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.werkzeug.http.parse_date(value) Parse an RFC 2822 date into a timezone-aware datetime.datetime object, or None if parsing fails.
This is a wrapper for email.utils.parsedate_to_datetime(). It returns None if parsing fails instead of raising an exception, and always returns a timezone-aware datetime object. If the string doesn’t have timezone information, it is assumed to be UTC.
value (str | None) – A string with a supported date format.
datetime | None
Changed in version 2.0: Return a timezone-aware datetime object. Use email.utils.parsedate_to_datetime.
werkzeug.http.http_date(timestamp=None) Format a datetime object or timestamp into an RFC 2822 date string.
This is a wrapper for email.utils.format_datetime(). It assumes naive datetime objects are in UTC instead of raising an exception.
timestamp (datetime | date | int | float | struct_time | None) – The datetime or timestamp to format. Defaults to the current time.
Changed in version 2.0: Use email.utils.format_datetime. Accept date objects.
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.
werkzeug.http.parse_options_header(value) Parse a header that consists of a value with key=value parameters separated by semicolons ;. For example, the Content-Type header.
parse_options_header("text/html; charset=UTF-8")
('text/html', {'charset': 'UTF-8'})
parse_options_header("")
("", {})
This is the reverse of dump_options_header().
This parses valid parameter parts as described in RFC 9110. Invalid parts are skipped.
This handles continuations and charsets as described in RFC 2231, although not as strictly as the RFC. Only ASCII, UTF-8, and ISO-8859-1 charsets are accepted, otherwise the value remains quoted.
Clients may not be consistent in how they handle a quote character within a quoted value. The HTML Standard replaces it with %22 in multipart form data. RFC 9110 uses backslash escapes in HTTP headers. Both are decoded to the " character.
Clients may not be consistent in how they handle non-ASCII characters. HTML documents must declare <meta charset=UTF-8>, otherwise browsers may replace with HTML character references, which can be decoded using html.unescape().
value (str | None) – The header value to parse.
(value, options), where options is a dict
Changed in version 2.3: Invalid parts, such as keys with no value, quoted keys, and incorrectly quoted values, are discarded instead of treating as None.
Changed in version 2.3: Only ASCII, UTF-8, and ISO-8859-1 are accepted for charset values.
Changed in version 2.3: Escaped quotes in quoted values, like %22 and \", are handled.
Changed in version 2.2: Option names are always converted to lowercase.
Changed in version 2.2: The multiple parameter was removed.
Changed in version 0.15: RFC 2231 parameter continuations are handled.
Added in version 0.5.
werkzeug.http.parse_set_header(value, on_update=None) Parse a set-like header and return a HeaderSet object:
>>> hs = parse_set_header('token, "quoted value"')
The return value is an object that treats the items case-insensitively and keeps the order of the items:
>>> 'TOKEN' in hs
True
>>> hs.index('quoted value')
1
>>> hs
HeaderSet(['token', 'quoted value'])
To create a header from the HeaderSet again, use the dump_header() function.
werkzeug.http.parse_list_header(value) Parse a header value that consists of a list of comma separated items according to RFC 9110.
This extends urllib.request.parse_http_list() to remove surrounding quotes from values.
parse_list_header('token, "quoted value"')
['token', 'quoted value']
This is the reverse of dump_header().
werkzeug.http.parse_dict_header(value) Parse a list header using parse_list_header(), then parse each item as a key=value pair.
parse_dict_header('a=b, c="d, e", f')
{"a": "b", "c": "d, e", "f": None}
This is the reverse of dump_header().
If a key does not have a value, it is None.
This handles charsets for values as described in RFC 2231. Only ASCII, UTF-8, and ISO-8859-1 charsets are accepted, otherwise the value remains quoted.
Changed in version 3.0: Passing bytes is not supported.
Changed in version 3.0: The cls argument is removed.
Changed in version 2.3: Added support for key*=charset''value encoded items.
Changed in version 0.9: The cls argument was added.
werkzeug.http.parse_accept_header(value: str | None) → Accept Parse an Accept header according to RFC 9110.
Returns an Accept instance, which can sort and inspect items based on their quality parameter. When parsing Accept-Charset, Accept-Encoding, or Accept-Language, pass the appropriate Accept subclass.
Accept class to wrap the result in.An instance of cls.
Changed in version 2.3: Parse according to RFC 9110. Items with invalid q values are skipped.
werkzeug.http.parse_cache_control_header(value: str | None, on_update: Callable[[_CacheControl], None] | None = None) → RequestCacheControl Parse a cache control header. The RFC differs between response and request cache control, this method does not. It’s your responsibility to not use the wrong control statements.
Added in version 0.5: The cls was added. If not specified an immutable RequestCacheControl is returned.
CacheControl object is changed.RequestCacheControl is used.a cls object.
werkzeug.http.parse_if_range_header(value) Parses an if-range header which can be an etag or a date. Returns a IfRange object.
Changed in version 2.0: If the value represents a datetime, it is timezone-aware.
Added in version 0.7.
werkzeug.http.parse_range_header(value, make_inclusive=True) Parses a range header into a Range object. If the header is missing or malformed None is returned. ranges is a list of (start, stop) tuples where the ranges are non-inclusive.
Added in version 0.7.
werkzeug.http.parse_content_range_header(value, on_update=None) Parses a range header into a ContentRange object or None if parsing is not possible.
Added in version 0.7.
ContentRange object is changed.ContentRange | None
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.
werkzeug.http.is_entity_header(header) Check if a header is an entity header.
Added in version 0.5.
werkzeug.http.is_hop_by_hop_header(header) Check if a header is an HTTP/1.1 “Hop-by-Hop” header.
Added in version 0.5.
werkzeug.http.remove_entity_headers(headers, allowed=('expires', 'content-location')) Remove all entity headers from a list or Headers object. This operation works in-place. Expires and Content-Location headers are by default not removed. The reason for this is RFC 2616 section 10.3.5 which specifies some entity headers that should be sent.
Changed in version 0.5: added allowed parameter.
werkzeug.http.remove_hop_by_hop_headers(headers) Remove all HTTP/1.1 “Hop-by-Hop” headers from a list or Headers object. This operation works in-place.
Added in version 0.5.
werkzeug.http.is_byte_range_valid(start, stop, length) Checks if a given byte content range is valid for the given length.
Added in version 0.7.
werkzeug.http.quote_header_value(value, allow_token=True) Add double quotes around a header value. If the header contains only ASCII token characters, it will be returned unchanged. If the header contains " or \ characters, they will be escaped with an additional \ character.
This is the reverse of unquote_header_value().
Changed in version 3.0: Passing bytes is not supported.
Changed in version 3.0: The extra_chars parameter is removed.
Changed in version 2.3: The value is quoted if it is the empty string.
Added in version 0.5.
werkzeug.http.unquote_header_value(value) Remove double quotes and decode slash-escaped " and \ characters in a header value.
This is the reverse of quote_header_value().
Changed in version 3.0: The is_filename parameter is removed.
werkzeug.http.dump_header(iterable) Produce a header value from a list of items or key=value pairs, separated by commas ,.
This is the reverse of parse_list_header(), parse_dict_header(), and parse_set_header().
If a value contains non-token characters, it will be quoted.
If a value is None, the key is output alone.
In some keys for some headers, a UTF-8 value can be encoded using a special key*=UTF-8''value form, where value is percent encoded. This function will not produce that format automatically, but if a given key ends with an asterisk *, the value is assumed to have that form and will not be quoted further.
dump_header(["foo", "bar baz"])
'foo, "bar baz"'
dump_header({"foo": "bar baz"})
'foo="bar baz"'
iterable (dict[str, Any] | Iterable[Any]) – The items to create a header from.
Changed in version 3.0: The allow_token parameter is removed.
Changed in version 2.2.3: If a key ends with *, its value will not be quoted.
For conditional responses the following functions might be useful:
werkzeug.http.parse_etags(value) Parse an etag header.
werkzeug.http.quote_etag(etag, weak=False) Quote an etag.
werkzeug.http.unquote_etag(etag: str) → tuple[str, bool] Unquote a single etag:
>>> unquote_etag('W/"bar"')
('bar', True)
>>> unquote_etag('"bar"')
('bar', False)
etag – the etag identifier to unquote.
a (etag, weak) tuple.
werkzeug.http.generate_etag(data) Generate an etag for some data.
Changed in version 2.0: Use SHA-1. MD5 may not be available in some environments.
werkzeug.http.is_resource_modified(environ, etag=None, data=None, last_modified=None, ignore_if_range=True) Convenience method for conditional requests.
generate_etag().False, If-Range header will be taken into account.True if the resource was modified, otherwise False.
Changed in version 2.0: SHA-1 is used to generate an etag value for the data. MD5 may not be available in some environments.
Changed in version 1.0.0: The check is run for methods other than GET and HEAD.
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.
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-urlencodedmultipart/form-dataNested 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.
class werkzeug.formparser.FormDataParser(stream_factory=None, max_form_memory_size=None, max_content_length=None, cls=None, silent=True, *, max_form_parts=None) This class implements parsing of form data for Werkzeug. By itself it can parse multipart and url encoded form data. It can be subclassed and extended but for most mimetypes it is a better idea to use the untouched stream and expose it as separate attributes on a request object.
Response._get_file_stream().RequestEntityTooLarge exception is raised.RequestEntityTooLarge exception is raised.None the default MultiDict is used.RequestEntityTooLarge exception is raised.Changed in version 3.0: The charset and errors parameters were removed.
Changed in version 3.0: The parse_functions attribute and get_parse_func methods were removed.
Changed in version 2.2.3: Added the max_form_parts parameter.
Added in version 0.8.
werkzeug.formparser.parse_form_data(environ, stream_factory=None, max_form_memory_size=None, max_content_length=None, cls=None, silent=True, *, max_form_parts=None) Parse the form data in the environ and return it as tuple in the form (stream, form, files). You should only call this method if the transport method is POST, PUT, or PATCH.
If the mimetype of the data transmitted is multipart/form-data the files multidict will be filled with FileStorage objects. If the mimetype is unknown the input stream is wrapped and returned as first argument, else the stream is empty.
This is a shortcut for the common usage of FormDataParser.
Response._get_file_stream().RequestEntityTooLarge exception is raised.RequestEntityTooLarge exception is raised.None the default MultiDict is used.RequestEntityTooLarge exception is raised.A tuple in the form (stream, form, files).
t_parse_result
Changed in version 3.0: The charset and errors parameters were removed.
Changed in version 2.3: Added the max_form_parts parameter.
Added in version 0.5.1: Added the silent parameter.
Added in version 0.5: Added the max_form_memory_size, max_content_length, and cls parameters.
© 2007 Pallets
Licensed under the BSD 3-clause License.
https://werkzeug.palletsprojects.com/en/latest/http/