HTTP Utilities — Werkzeug 0.9.4 documentation

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# 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.

## Date Functions

The following functions simplify working with times in an HTTP context. Werkzeug uses offset-naive `datetime` objects internally that store the time in UTC. If you’re working with timezones in your application make sure to replace the tzinfo attribute with a UTC timezone information before processing the values.

`werkzeug.http.` `cookie_date`(expires=None)

  Formats the time to ensure compatibility with Netscape’s cookie standard.

  Accepts a floating point number expressed in seconds since the epoch in, a datetime object or a timetuple. All times in UTC. The `parse_date()` function can be used to parse such a date.

  Outputs a string in the format `Wdy, DD-Mon-YYYY HH:MM:SS GMT`.

  Parameters: | expires – If provided that date is used, otherwise the current.

`werkzeug.http.` `http_date`(timestamp=None)

  Formats the time to match the RFC1123 date format.

  Accepts a floating point number expressed in seconds since the epoch in, a datetime object or a timetuple. All times in UTC. The `parse_date()` function can be used to parse such a date.

  Outputs a string in the format `Wdy, DD Mon YYYY HH:MM:SS GMT`.

  Parameters: | timestamp – If provided that date is used, otherwise the current.

`werkzeug.http.` `parse_date`(value)

  Parse one of the following date formats into a datetime object:

      Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
      Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
      Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format

  If parsing fails the return value is None.

  Parameters: | value – a string with a supported date format.
  Returns: | a `datetime.datetime` object.

## 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.

`werkzeug.http.` `parse_options_header`(value)

  Parse a `Content-Type` like header into a tuple with the content type and the options:

      >>> parse_options_header('text/html; charset=utf8')
      ('text/html', {'charset': 'utf8'})

  This should not be used to parse `Cache-Control` like headers that use a slightly different format. For these headers use the `parse_dict_header()` function.

  New in version 0.5.

  Parameters: | value – the header to parse.
  Returns: | (str, options)

`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.

  Parameters: | value – a set header to be parsed. on_update – an optional callable that is called every time a value on the `HeaderSet` object is changed.
  Returns: | a `HeaderSet`

`werkzeug.http.` `parse_list_header`(value)

  Parse lists as described by RFC 2068 Section 2.

  In particular, parse comma-separated lists where the elements of the list may include quoted-strings. A quoted-string could contain a comma. A non-quoted string could have quotes in the middle. Quotes are removed automatically after parsing.

  It basically works like `parse_set_header()` just that items may appear multiple times and case sensitivity is preserved.

  The return value is a standard `list`:

      >>> parse_list_header('token, "quoted value"')
      ['token', 'quoted value']

  To create a header from the `list` again, use the `dump_header()` function.

  Parameters: | value – a string with a list header.
  Returns: | `list`

`werkzeug.http.` `parse_dict_header`(value, cls=<type 'dict'>)

  Parse lists of key, value pairs as described by RFC 2068 Section 2 and convert them into a python dict (or any other mapping object created from the type with a dict like interface provided by the cls arugment):

      >>> d = parse_dict_header('foo="is a fish", bar="as well"')
      >>> type(d) is dict
      True
      >>> sorted(d.items())
      [('bar', 'as well'), ('foo', 'is a fish')]

  If there is no value for a key it will be None:

      >>> parse_dict_header('key_without_value')
      {'key_without_value': None}

  To create a header from the `dict` again, use the `dump_header()` function.

  Changed in version 0.9: Added support for cls argument.

  Parameters: | value – a string with a dict header. cls – callable to use for storage of parsed results.
  Returns: | an instance of cls

`werkzeug.http.` `parse_accept_header`(value[, class])

  Parses an HTTP Accept-* header. This does not implement a complete valid algorithm but one that supports at least value and quality extraction.

  Returns a new `Accept` object (basically a list of `(value, quality)` tuples sorted by the quality with some additional accessor methods).

  The second parameter can be a subclass of `Accept` that is created with the parsed values and returned.

  Parameters: | value – the accept header string to be parsed. cls – the wrapper class for the return value (can be `Accept` or a subclass thereof)
  Returns: | an instance of cls.

`werkzeug.http.` `parse_cache_control_header`(value, on_update=None, cls=None)

  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.

  New in version 0.5: The cls was added. If not specified an immutable `RequestCacheControl` is returned.

  Parameters: | value – a cache control header to be parsed. on_update – an optional callable that is called every time a value on the `CacheControl` object is changed. cls – the class for the returned object. By default `RequestCacheControl` is used.
  Returns: | a cls object.

`werkzeug.http.` `parse_authorization_header`(value)

  Parse an HTTP basic/digest authorization header transmitted by the web browser. The return value is either None if the header was invalid or not given, otherwise an `Authorization` object.

  Parameters: | value – the authorization header to parse.
  Returns: | a `Authorization` object or None.

`werkzeug.http.` `parse_www_authenticate_header`(value, on_update=None)

  Parse an HTTP WWW-Authenticate header into a `WWWAuthenticate` object.

  Parameters: | value – a WWW-Authenticate header to parse. on_update – an optional callable that is called every time a value on the `WWWAuthenticate` object is changed.
  Returns: | a `WWWAuthenticate` 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.

  New 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.

  New 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.

  New in version 0.7.

  Parameters: | value – a content range header to be parsed. on_update – an optional callable that is called every time a value on the `ContentRange` object is changed.

## 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.

`werkzeug.http.` `is_entity_header`(header)

  Check if a header is an entity header.

  New in version 0.5.

  Parameters: | header – the header to test.
  Returns: | True if it’s an entity header, False otherwise.

`werkzeug.http.` `is_hop_by_hop_header`(header)

  Check if a header is an HTTP/1.1 “Hop-by-Hop” header.

  New in version 0.5.

  Parameters: | header – the header to test.
  Returns: | True if it’s an entity header, False otherwise.

`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.

  Parameters: | headers – a list or `Headers` object. allowed – a list of headers that should still be allowed even though they are entity headers.

`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.

  New in version 0.5.

  Parameters: | headers – a list or `Headers` object.

`werkzeug.http.` `is_byte_range_valid`(start, stop, length)

  Checks if a given byte content range is valid for the given length.

  New in version 0.7.

`werkzeug.http.` `quote_header_value`(value, extra_chars='', allow_token=True)

  Quote a header value if necessary.

  New in version 0.5.

  Parameters: | value – the value to quote. extra_chars – a list of extra characters to skip quoting. allow_token – if this is enabled token values are returned unchanged.

`werkzeug.http.` `unquote_header_value`(value, is_filename=False)

  Unquotes a header value. (Reversal of `quote_header_value()`). This does not use the real unquoting but what browsers are actually using for quoting.

  New in version 0.5.

  Parameters: | value – the header value to unquote.

`werkzeug.http.` `dump_header`(iterable, allow_token=True)

  Dump an HTTP header again. This is the reversal of `parse_list_header()`, `parse_set_header()` and `parse_dict_header()`. This also quotes strings that include an equals sign unless you pass it as dict of key, value pairs.

      >>> dump_header({'foo': 'bar baz'})
      'foo="bar baz"'
      >>> dump_header(('foo', 'bar baz'))
      'foo, "bar baz"'

  Parameters: | iterable – the iterable or dict of values to quote. allow_token – if set to False tokens as values are disallowed. See `quote_header_value()` for more details.

## Cookies

`werkzeug.http.` `parse_cookie`(header, charset='utf-8', errors='replace', cls=None)

  Parse a cookie. Either from a string or WSGI environ.

  Per default encoding errors are ignored. If you want a different behavior you can set errors to `'replace'` or `'strict'`. In strict mode a `HTTPUnicodeError` is raised.

  Changed in version 0.5: This function now returns a `TypeConversionDict` instead of a regular dict. The cls parameter was added.

  Parameters: | header – the header to be used to parse the cookie. Alternatively this can be a WSGI environment. charset – the charset for the cookie values. errors – the error behavior for the charset decoding. cls – an optional dict class to use. If this is not specified or None the default `TypeConversionDict` is used.

`werkzeug.http.` `dump_cookie`(key, value='', max_age=None, expires=None, path='/', domain=None, secure=False, httponly=False, charset='utf-8', sync_expires=True)

  Creates a new Set-Cookie header without the `Set-Cookie` prefix The parameters are the same as in the cookie Morsel object in the Python standard library but it accepts unicode data, too.

  On Python 3 the return value of this function will be a unicode string, on Python 2 it will be a native string. In both cases the return value is usually restricted to ascii as the vast majority of values are properly escaped, but that is no guarantee. If a unicode string is returned it’s tunneled through latin1 as required by PEP 3333.

  The return value is not ASCII safe if the key contains unicode characters. This is technically against the specification but happens in the wild. It’s strongly recommended to not use non-ASCII values for the keys.

  Parameters: | max_age – should be a number of seconds, or None (default) if the cookie should last only as long as the client’s browser session. Additionally timedelta objects are accepted, too. expires – should be a datetime object or unix timestamp. path – limits the cookie to a given path, per default it will span the whole domain. domain – Use this if you want to set a cross-domain cookie. For example, `domain=".example.com"` will set a cookie that is readable by the domain `www.example.com`, `foo.example.com` etc. Otherwise, a cookie will only be readable by the domain that set it. secure – The cookie will only be available via HTTPS httponly – disallow JavaScript to access the cookie. This is an extension to the cookie standard and probably not supported by all browsers. charset – the encoding for unicode values. sync_expires – automatically set expires if max_age is defined but expires not.

## Conditional Response Helpers

For conditional responses the following functions might be useful:

`werkzeug.http.` `parse_etags`(value)

  Parse an etag header.

  Parameters: | value – the tag header to parse
  Returns: | an `ETags` object.

`werkzeug.http.` `quote_etag`(etag, weak=False)

  Quote an etag.

  Parameters: | etag – the etag to quote. weak – set to True to tag it “weak”.

`werkzeug.http.` `unquote_etag`(etag)

  Unquote a single etag:

      >>> unquote_etag('w/"bar"')
      ('bar', True)
      >>> unquote_etag('"bar"')
      ('bar', False)

  Parameters: | etag – the etag identifier to unquote.
  Returns: | a `(etag, weak)` tuple.

`werkzeug.http.` `generate_etag`(data)

  Generate an etag for some data.

`werkzeug.http.` `is_resource_modified`(environ, etag=None, data=None, last_modified=None)

  Convenience method for conditional requests.

  Parameters: | environ – the WSGI environment of the request to be checked. etag – the etag for the response for comparison. data – or alternatively the data of the response to automatically generate an etag using `generate_etag()`. last_modified – an optional date of the last modification.
  Returns: | True if the resource was modified, otherwise False.

## 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 cStringIO import StringIO
    >>> data = '--foo\r\nContent-Disposition: form-data; name="test"\r\n' \
    ... '\r\nHello World!\r\n--foo--'
    >>> environ = {'wsgi.input': StringIO(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()
    ''
    >>> form['test']
    u'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, charset='utf-8', errors='replace', max_form_memory_size=None, max_content_length=None, cls=None, silent=True)

  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.

  New in version 0.8.

  Parameters: | stream_factory – An optional callable that returns a new read and writeable file descriptor. This callable works the same as `_get_file_stream()`. charset – The character set for URL and url encoded form data. errors – The encoding error behavior. max_form_memory_size – the maximum number of bytes to be accepted for in-memory stored form data. If the data exceeds the value specified an `RequestEntityTooLarge` exception is raised. max_content_length – If this is provided and the transmitted data is longer than this value an `RequestEntityTooLarge` exception is raised. cls – an optional dict class to use. If this is not specified or None the default `MultiDict` is used. silent – If set to False parsing errors will not be caught.

`werkzeug.formparser.` `parse_form_data`(environ, stream_factory=None, charset='utf-8', errors='replace', max_form_memory_size=None, max_content_length=None, cls=None, silent=True)

  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`.

  Have a look at Dealing with Request Data for more details.

  New in version 0.5: The max_form_memory_size, max_content_length and cls parameters were added.

  New in version 0.5.1: The optional silent flag was added.

  Parameters: | environ – the WSGI environment to be used for parsing. stream_factory – An optional callable that returns a new read and writeable file descriptor. This callable works the same as `_get_file_stream()`. charset – The character set for URL and url encoded form data. errors – The encoding error behavior. max_form_memory_size – the maximum number of bytes to be accepted for in-memory stored form data. If the data exceeds the value specified an `RequestEntityTooLarge` exception is raised. max_content_length – If this is provided and the transmitted data is longer than this value an `RequestEntityTooLarge` exception is raised. cls – an optional dict class to use. If this is not specified or None the default `MultiDict` is used. silent – If set to False parsing errors will not be caught.
  Returns: | A tuple in the form `(stream, form, files)`.

`werkzeug.formparser.` `parse_multipart_headers`(iterable)

  Parses multipart headers from an iterable that yields lines (including the trailing newline symbol). The iterable has to be newline terminated.

  The iterable will stop at the line where the headers ended so it can be further consumed.

  Parameters: | iterable – iterable of strings that are newline terminated