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WSGI, CLI scripts

Working with wsgiwrappers.WSGIRequest

Pylons uses a specialised WSGIRequest class that is accessible via the paste.wsgiwrappers module.

The wsgiwrappers.WSGIRequest object represents a WSGI request that has a more programmer-friendly interface. This interface does not expose every detail of the WSGI environment (why?) and does not attempt to express anything beyond what is available in the environment dictionary.

The only state maintained in this object is the desired charset, an associated errors handler and a decode_param_names option.

Unicode notes

When charset is set, the incoming parameter values will be automatically coerced to unicode objects of the charset encoding.

When unicode is expected, charset will be overridden by the the value of the charset parameter set in the Content-Type header, if one was specified by the client.

The incoming parameter names are not decoded to unicode unless the decode_param_names option is enabled.

The class variable defaults specifies default values for charset, errors, and language. These default values can be overridden for the current request via the registry (what’s a registry?).

The language default value is considered the fallback during i18n translations to ensure in odd cases that mixed languages don’t occur should the language file contain the string but not another language in the accepted languages list. The language value only applies when getting a list of accepted languages from the HTTP Accept header.

This behavior is duplicated from Aquarium, and may seem strange but is very useful. Normally, everything in the code is in “en-us”. However, the “en-us” translation catalog is usually empty. If the user requests [“en-us”, “zh-cn”] and a translation isn’t found for a string in “en-us”, you don’t want gettext to fallback to “zh-cn”. You want it to just use the string itself. Hence, if a string isn’t found in the language catalog, the string in the source code will be used.

All other state is kept in the environment dictionary; this is essential for interoperability.

You are free to subclass this object.



A dictionary-like object representing the QUERY_STRING parameters. Always present, possibly empty.

If the same key is present in the query string multiple times, a list of its values can be retrieved from the MultiDict via the :meth:getall method.

Returns a MultiDict container or, when charset is set, a UnicodeMultiDict.


A dictionary-like object representing the POST body.

Most values are encoded strings, or unicode strings when charset is set. There may also be FieldStorage objects representing file uploads. If this is not a POST request, or the body is not encoded fields (e.g., an XMLRPC request) then this will be empty.

This will consume wsgi.input when first accessed if applicable, but the raw version will be put in environ[‘paste.parsed_formvars’].

Returns a MultiDict container or a UnicodeMultiDict when charset is set.


A dictionary of cookies, keyed by cookie name.

Just a plain dictionary, may be empty but not None.


{'errors': 'replace',
 'decode_param_names': False,
 'charset': None,
 'language': 'en-us'}


The host name, as provided in HTTP_HOST with a fall-back to SERVER_NAME


Returns a boolean if X-Requested-With is present and is a XMLHttpRequest


Returns a (possibly empty) list of preferred languages, most preferred first.


A dictionary-like object of keys from POST, GET, URL dicts

Return a key value from the parameters, they are checked in the following order: POST, GET, URL

Additional methods supported:


Returns a list of all the values by that key, collected from POST, GET, URL dicts

Returns a MultiDict container or a UnicodeMultiDict when charset is set.


Return any variables matched in the URL (e.g. wsgiorg.routing_args).


__init__(self, environ)


Determine the encoding as specified by the browser via the Content-Type’s charset parameter, if one is set

match_accept(self, mimetypes)

Return a list of specified mime-types that the browser’s HTTP Accept header allows in the order provided.