WSGI 1.0 Cheat-sheet

Authors Gustavo Narea

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WSGI 1.0 Cheat-sheet
• REMOTE_USER: If the user that made the request response headers. It takes two positional arguments: The
Definitions HTTP status string (e.g., “200 OK”) and a list made up of
has been authenticated successfully (in this request or
• Server: HTTP server that has Python embedded (or tuples whose first element is the header name and the
in a previous one), this variable represents his unique
it's itself a Python application), and calls the WSGI user identifier (e.g., a name). second is the header value.
application callable directly.
• HTTP_* variables: Those present in the HTTP It returns a callable which can be used by legacy
• Gateway: Server-independent Python-powered request, in upper case and with hyphens replaced applications to send the body (aka write() callable), if
application that calls the WSGI application callable with underscores. For example, User-Agent becomes they cannot return an iterable. It can be called multiple
directly and “connects” it to the Web server. HTTP_USER_AGENT. times and its only argument is a string to be sent.
• Application: The WSGI application callable. • wsgi.input: The file-like object that contains the File wrapper
• Middleware: Callable that wraps one or more WSGI body of the request.
applications, to filter their requests and/or responses. If the server or gateway supports a high performance
• wsgi.url_scheme: The scheme portion of the URL method to send files, it'd be available in the WSGI
(“http” or “https”).
WSGI environ variables environ as “wsgi.file_wrapper”.
There are many variables, but the following are possibly API It's a callable that takes one mandatory argument (the
the most commonly used ones when you want to do file-like object whose contents should be sent) and an
something simple yet low-level without a framework: WSGI application optional size hint (the amount of bytes that should be sent
It can be any callable. It takes two positional arguments, at the same time).
• REQUEST_METHOD: The HTTP request method
(e.g., “POST”, “GET”, “HEAD”, “PUT”). the WSGI environ and the server-provided
start_response() callable. To send a response,
wsgi.errors
• SCRIPT_NAME: The portion of the URL path that A file-like object in the WSGI environ where non-fatal
start_response() must be called to send the headers first
is not consumed by the application. For example, if errors should be written. The messages are usually sent to
and then an iterable representing the body must be
you have Trac running on http://example.org/trac/, the server's main error log.
returned.
the script name for Trac will always be “/trac”. If
Trac is running on http://example.org/ then the script WSGI middleware Links
name is an empty string. • Web-SIG: The best place to ask WSGI-related
WSGI middleware must be a callable with the same API
• PATH_INFO: The portion of the URL path that is as a WSGI application. Servers or gateways must not try questions:
consumed by the application. For example, if you to distinguish an application from a piece of middleware. http://mail.python.org/mailman/listinfo/web-sig
have Trac running on http://example.org/trac/, the http://wsgi.org/
path info for Trac will always be everything after WSGI environ • PEP-333: http://www.python.org/dev/peps/pep-0333/
“/trac”. It is the path info is the part of the URL path A dict instance. Not a dictionary-like object.
not use by the script name. WSGI “shops”
• QUERY_STRING: The URL-encoded string that start_response()
• Paste: http://www.pythonpaste.org
contains the so-called “GET arguments”. If set, it A callable provided by the server or gateway on every
comes after the question mark in URLs. request, used by the WSGI application to send its • Repoze: http://www.repoze.org/