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Title: wsgiref — WSGI Utilities and Reference Implementation — Python 3.13.18 documentation
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ABSTRACT
wsgiref — WSGI Utilities and Reference Implementation — Python 3.13.18 documentation Navigation index modules | next | previous | Python » 3.13.18 Documentation » The Python standard library » Internet Protocols and Support » wsgiref — WSGI Utilities and Reference Implementation | Theme Auto Light Dark | wsgiref — WSGI Utilities and Reference Implementation¶ Source code: Lib/wsgiref Warning wsgiref is a reference implementation and is not recommended for production. The module only implements basic security checks. The Web Server Gateway Interface (WSGI) is a standard interface between web server software and web applications written in Python. Having a standard interface makes it easy to use an application that supports WSGI with a number of different web servers. Only authors of web servers and programming frameworks need to know every detail and corner case of the WSGI design. You don’t need to understand every detail of WSGI just to install a WSGI application or to write a web application using an existing framework. wsgiref is a reference implementation of the WSGI specification that can be used to add WSGI support to a web server or framework. It provides utilities for manipulating WSGI environment variables and response headers, base classes for implementing WSGI servers, a demo HTTP server that serves WSGI applications, types for static type checking, and a validation tool that checks WSGI servers and applications for conformance to the WSGI specification (PEP 3333). See wsgi.readthedocs.io for more information about WSGI, and links to tutorials and other resources. wsgiref.util – WSGI environment utilities¶ This module provides a variety of utility functions for working with WSGI environments. A WSGI environment is a dictionary containing HTTP request variables as described in PEP 3333. All of the functions taking an environ parameter expect a WSGI-compliant dictionary to be supplied; please see PEP 3333 for a detailed specification and WSGIEnvironment for a type alias that can be used in type annotations. wsgiref.util.guess_scheme(environ)¶ Return a guess for whether wsgi.url_scheme should be “http” or “https”, by checking for a HTTPS environment variable in the environ dictionary. The return value is a string. This function is useful when creating a gateway that wraps CGI or a CGI-like protocol such as FastCGI. Typically, servers providing such protocols will include a HTTPS variable with a value of “1”, “yes”, or “on” when a request is received via SSL. So, this function returns “https” if such a value is found, and “http” otherwise. wsgiref.util.request_uri(environ, include_query=True)¶ Return the full request URI, optionally including the query string, using the algorithm found in the “URL Reconstruction” section of PEP 3333. If include_query is false, the query string is not included in the resulting URI. wsgiref.util.application_uri(environ)¶ Similar to request_uri(), except that the PATH_INFO and QUERY_STRING variables are ignored. The result is the base URI of the application object addressed by the request. wsgiref.util.shift_path_info(environ)¶ Shift a single name from PATH_INFO to SCRIPT_NAME and return the name. The environ dictionary is modified in-place; use a copy if you need to keep the original PATH_INFO or SCRIPT_NAME intact. If there are no remaining path segments in PATH_INFO, None is returned. Typically, this routine is used to process each portion of a request URI path, for example to treat the path as a series of dictionary keys. This routine modifies the passed-in environment to make it suitable for invoking another WSGI application that is located at the target URI. For example, if there is a WSGI application at /foo, and the request URI path is /foo/bar/baz, and the WSGI application at /foo calls shift_path_info(), it will receive the string “bar”, and the environment will be updated to be suitable for passing to a WSGI application at /foo/bar. That is, SCRIPT_NAME will change from /foo to /foo/bar, and PATH_INFO will change from /bar/baz to /baz. When PATH_INFO is just a “/”, this routine returns an empty string and appends a trailing slash to SCRIPT_NAME, even though empty path segments are normally ignored, and SCRIPT_NAME doesn’t normally end in a slash. This is intentional behavior, to ensure that an application can tell the difference between URIs ending in /x from ones ending in /x/ when using this routine to do object traversal. wsgiref.util.setup_testing_defaults(environ)¶ Update environ with trivial defaults for testing purposes. This routine adds various parameters required for WSGI, including HTTP_HOST, SERVER_NAME, SERVER_PORT, REQUEST_METHOD, SCRIPT_NAME, PATH_INFO, and all of the PEP 3333-defined wsgi.* variables. It only supplies default values, and does not replace any existing settings for these variables. This routine is intended to make it easier for unit tests of WSGI servers and applications to set up dummy environments. It should NOT be used by actual WSGI servers or applications, since the data is fake! Example usage (see also demo_app() for another example): from wsgiref.util import setup_testing_defaults from wsgiref.simple_server import make_server # A relatively simple WSGI application. It's going to print out the # environment dictionary after being updated by setup_testing_defaults def simple_app(environ, start_response): setup_testing_defaults(environ) status = '200 OK' headers = [('Content-type', 'text/plain; charset=utf-8')] start_response(status, headers) ret = [("%s: %s\n" % (key, value)).encode("utf-8") for key, value in environ.items()] return ret with make_server('', 8000, simple_app) as httpd: print("Serving on port 8000...") httpd.serve_forever() In addition to the environment functions above, the wsgiref.util module also provides these miscellaneous utilities: wsgiref.util.is_hop_by_hop(header_name)¶ Return True if ‘header_name’ is an HTTP/1.1 “Hop-by-Hop” header, as defined by RFC 2616. class wsgiref.util.FileWrapper(filelike, blksize=8192)¶ A concrete implementation of the wsgiref.types.FileWrapper protocol used to convert a file-like object to an iterator. The resulting objects are iterables. As the object is iterated over, the optional blksize parameter will be repeatedly passed to the filelike object’s read() method to obtain bytestrings to yield. When read() returns an empty bytestring, iteration is ended and is not resumable. If filelike has a close() method, the returned object will also have a close() method, and it will invoke the filelike object’s close() method when called. Example usage: from io import StringIO from wsgiref.util import FileWrapper # We're using a StringIO-buffer for as the file-like object filelike = StringIO("This is an example file-like object"*10) wrapper = FileWrapper(filelike, blksize=5) for chunk in wrapper: print(chunk) Changed in version 3.11: Support for __getitem__() method has been removed. wsgiref.headers – WSGI response header tools¶ This module provides a single class, Headers, for convenient manipulation of WSGI response headers using a mapping-like interface. class wsgiref.headers.Headers([headers])¶ Create a mapping-like object wrapping headers, which must be a list of header name/value tuples as described in PEP 3333. The default value of headers is an empty list. Headers objects support typical mapping operations including __getitem__(), get(), __setitem__(), setdefault(), __delitem__() and __contains__(). For each of these methods, the key is the header name (treated case-insensitively), and the value is the first value associated with that header name. Setting a header deletes any existing values for that header, then adds a new value at the end of the wrapped header list. Headers’ existing order is generally maintained, with new headers added to the end of the wrapped list. Unlike a dictionary, Headers objects do not raise an error when you try to get or delete a key that isn’t in the wrapped header list. Getting a nonexistent header just returns None, and deleting a nonexistent header does nothing. Headers objects also support keys(), values(), and items() methods. The lists returned by keys() and items() can include the same key more than once if there is a multi-valued header. The len() of a Headers object is the same as the length of its items(), which is the same as the length of the wrapped header list. In fact, the items() method just returns a copy of the wrapped header list. Calling bytes() on a Headers object returns a formatted bytestring suitable for transmission as HTTP response headers. Each header is placed on a line with its value, separated by a colon and a space. Each line is terminated by a carriage return and line feed, and the bytestring is terminated with a blank line. In addition to their mapping interface and formatting features, Headers objects also have the following methods for querying and adding multi-valued headers, and for adding headers with MIME parameters: get_all(name)¶ Return a list of all the values for the named header. The returned list will be sorted in the order they appeared in the original header list or were added to this instance, and may contain duplicates. Any fields deleted and re-inserted are always appended to the header list. If no fields exist with the given name, returns an empty list. add_header(name, value, **_params)¶ Add a (possibly multi-valued) header, with optional MIME parameters specified via keyword arguments. name is the header field to add. Keyword arguments can be used to set MIME parameters for the header field. Each parameter must be a string or None. Underscores in parameter names are converted to dashes, since dashes are illegal in Python identifiers, but many MIME parameter names include dashes. If the parameter value is a string, it is added to the header value parameters in the form name="value". If it is None, only the parameter name is added. (This is used for MIME parameters without a value.) Example usage: h.add_header('content-disposition', 'attachment', filename='bud.gif') The above will add a header that looks like this: Content-Disposition: attachment; filename="bud.gif" Changed in version 3.5: headers parameter is optional. wsgiref.simple_server – a simple WSGI HTTP server¶ This module implements a simple HTTP server (based on http.server) that serves WSGI applications. Each server instance serves a single WSGI application on a given host and port. If you want to serve multiple applications on a single host and port, you should create a WSGI application that parses PATH_INFO to select which application to invoke for each request. (E.g., using the shift_path_info() function from wsgiref.util.) wsgiref.simple_server.make_server(host, port, app, server_class=WSGIServer, handler_class=WSGIRequestHandler)¶ Create a new WSGI server listening on host and port, accepting connections for app. The return value is an instance of the supplied server_class, and will process requests using the specified handler_class. app must be a WSGI application object, as defined by PEP 3333. Example usage: from wsgiref.simple_server import make_server, demo_app with make_server('', 8000, demo_app) as httpd: print("Serving HTTP on port 8000...") # Respond to requests until process is killed httpd.serve_forever() # Alternative: serve one request, then exit httpd.handle_request() wsgiref.simple_server.demo_app(environ, start_response)¶ This function is a small but complete WSGI application that returns a text page containing the message “Hello world!” and a list of the key/value pairs provided in the environ parameter. It’s useful for verifying that a WSGI server (such as wsgiref.simple_server) is able to run a simple WSGI application correctly. The start_response callable should follow the StartResponse protocol. class wsgiref.simple_server.WSGIServer(server_address, RequestHandlerClass)¶ Create a WSGIServer instance. server_address should be a (host,port) tuple, and RequestHandlerClass should be the subclass of http.server.BaseHTTPRequestHandler that will be used to process requests. You do not normally need to call this constructor, as the make_server() function can handle all the details for you. WSGIServer is a subclass of http.server.HTTPServer, so all of its methods (such as serve_forever() and handle_request()) are available. WSGIServer also provides these WSGI-specific methods: set_app(application)¶ Sets the callable application as the WSGI application that will receive requests. get_app()¶ Returns the currently set application callable. Normally, however, you do not need to use these additional methods, as set_app() is normally called by make_server(), and the get_app() exists mainly for the benefit of request handler instances. class wsgiref.simple_server.WSGIRequestHandler(request, client_address, server)¶ Create an HTTP handler for the given request (i.e. a socket), client_address (a (host,port) tuple), and server (WSGIServer instance). You do not need to create instances of this class directly; they are automatically created as needed by WSGIServer objects. You can, however, subclass this class and supply it as a handler_class to the make_server() function. Some possibly relevant methods for overriding in subclasses: get_environ()¶ Return a WSGIEnvironment dictionary for a request. The default implementation copies the contents of the WSGIServer object’s base_environ dictionary attribute and then adds various headers derived from the HTTP request. Each call to this method should return a new dictionary containing all of the relevant CGI environment variables as specified in PEP 3333. get_stderr()¶ Return the object that should be used as the wsgi.errors stream. The default implementation just returns sys.stderr. handle()¶ Process the HTTP request. The default implementation creates a handler instance using a wsgiref.handlers class to implement the actual WSGI application interface. wsgiref.validate — WSGI conformance checker¶ When creating new WSGI application objects, frameworks, servers, or middleware, it can be useful to validate the new code’s conformance using wsgiref.validate. This module provides a function that creates WSGI application objects that validate communications between a WSGI server or gateway and a WSGI application object, to check both sides for protocol conformance. Note that this utility does not guarantee complete PEP 3333 compliance; an absence of errors from this module does not necessarily mean that errors do not exist. However, if this module does produce an error, then it is virtually certain that either the server or application is not 100% compliant. This module is based on the paste.lint module from Ian Bicking’s “Python Paste” library. wsgiref.validate.validator(application)¶ Wrap application and return a new WSGI application object. The returned application will forward all requests to the original application, and will check that both the application and the server invoking it are conforming to the WSGI specification and to RFC 2616. Any detected nonconformance results in an AssertionError being raised; note, however, that how these errors are handled is server-dependent. For example, wsgiref.simple_server and other servers based on wsgiref.handlers (that don’t override the error handling methods to do something else) will simply output a message that an error has occurred, and dump the traceback to sys.stderr or some other error stream. This wrapper may also generate output using the warnings module to indicate behaviors that are questionable but which may not actually be prohibited by PEP 3333. Unless they are suppressed using Python command-line options or the warnings API, any such warnings will be written to sys.stderr (not wsgi.errors, unless they happen to be the same object). Example usage: from wsgiref.validate import validator from wsgiref.simple_server import make_server # Our callable object which is intentionally not compliant to the # standard, so the validator is going to break def simple_app(environ, start_response): status = '200 OK' # HTTP Status headers = [('Content-type', 'text/plain')] # HTTP Headers start_response(status, headers) # This is going to break because we need to return a list, and # the validator is going to inform us return b"Hello World" # This is the application wrapped in a validator validator_app = validator(simple_app) with make_server('', 8000, validator_app) as httpd: print("Listening on port 8000....") httpd.serve_forever() wsgiref.handlers – server/gateway base classes¶ This module provides base handler classes for implementing WSGI servers and gateways. These base classes handle most of the work of communicating with a WSGI application, as long as they are given a CGI-like environment, along with input, output, and error streams. class wsgiref.handlers.CGIHandler¶ CGI-based invocation via sys.stdin, sys.stdout, sys.stderr and os.environ. This is useful when you have a WSGI application and want to run it as a CGI script. Simply invoke CGIHandler().run(app), where app is the WSGI application object you wish to invoke. This class is a subclass of BaseCGIHandler that sets wsgi.run_once to true, wsgi.multithread to false, and wsgi.multiprocess to true, and always uses sys and os to obtain the necessary CGI streams and environment. class wsgiref.handlers.IISCGIHandler¶ A specialized alternative to CGIHandler, for use when deploying on Microsoft’s IIS web server, without having set the config allowPathInfo option (IIS=7) or metabase allowPathInfoForScriptMappings (IIS 1 else os.getcwd() port = int(sys.argv[2]) if len(sys.argv) 2 else 8000 # Make and start the server until control-c httpd = simple_server.make_server("", port, app) print(f"Serving {path} on port {port}, control-C to stop") try: httpd.serve_forever() except KeyboardInterrupt: print("Shutting down.") httpd.server_close() Table of Contents wsgiref — WSGI Utilities and Reference Implementation wsgiref.util – WSGI environment utilities wsgiref.headers – WSGI response header tools wsgiref.simple_server – a simple WSGI HTTP server wsgiref.validate — WSGI conformance checker wsgiref.handlers – server/gateway base classes wsgiref.types – WSGI types for static type checking Examples Previous topic webbrowser — Convenient web-browser controller Next topic urllib — URL handling modules This page Report a bug Show source « Navigation index modules | next | previous | Python » 3.13.18 Documentation » The Python standard library » Internet Protocols and Support » wsgiref — WSGI Utilities and Reference Implementation | Theme Auto Light Dark | © Copyright 2001-2026, Python Software Foundation. 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