Lib/wsgiref/handlers.py

Source:

cpython 3.14 @ ab2d84fe1023/Lib/wsgiref/handlers.py ↗

wsgiref.handlers implements the WSGI gateway (PEP 3333). BaseHandler.run(app) calls the WSGI application and sends the response headers and body to the transport.

Map

Lines	Symbol	Role
1-80	BaseHandler	Abstract base: run, start_response, write, finish_response
81-200	SimpleHandler	Concrete handler with stdin, stdout, stderr streams
201-350	BaseCGIHandler	CGI: write response to sys.stdout
351-450	WSGIRequestHandler	Subclass for http.server.BaseHTTPRequestHandler
451-500	make_server	Create a WSGIServer bound to an address

Reading

BaseHandler.run

# CPython: Lib/wsgiref/handlers.py:98 BaseHandler.run
def run(self, application):
    """Invoke the WSGI application and send the response."""
    try:
        self.setup_environ()
        self.result = application(self.environ, self.start_response)
        self.finish_response()
    except:
        try:
            self.handle_error()
        except:
            self.close()
            raise

start_response

# CPython: Lib/wsgiref/handlers.py:140 BaseHandler.start_response
def start_response(self, status, headers, exc_info=None):
    """WSGI start_response callable: record status and headers."""
    if exc_info:
        try:
            if self.headers_sent:
                reraise(*exc_info)
        finally:
            exc_info = None
    elif self.headers is not None:
        raise AssertionError("Headers already set!")
    self.status = status
    self.headers = self.headers_class(headers)
    return self.write

start_response is called once by the WSGI application before any body is written. It returns the write callable for legacy apps.

write

# CPython: Lib/wsgiref/handlers.py:175 BaseHandler.write
def write(self, data):
    """Write data to the response.  Called by legacy WSGI apps."""
    assert isinstance(data, bytes), "write() argument must be a bytes instance"
    if not self.status:
        raise AssertionError("write() before start_response()")
    elif not self.headers_sent:
        self.send_headers()
    self._write(data)    # delegates to transport
    self._flush()

finish_response

# CPython: Lib/wsgiref/handlers.py:200 BaseHandler.finish_response
def finish_response(self):
    """Send the response body from the WSGI result iterable."""
    try:
        for data in self.result:
            self.write(data)
        self.finish_content()
    except:
        self.close()
        raise
    else:
        self.close()

WSGI result must be an iterable of bytes objects.

make_server

# CPython: Lib/wsgiref/simple_server.py:120 make_server
def make_server(host, port, app, server_class=WSGIServer,
                handler_class=WSGIRequestHandler):
    """Create a WSGI server for testing purposes."""
    server = server_class((host, port), handler_class)
    server.set_app(app)
    return server

gopy notes

wsgiref is pure Python and works with gopy's http.server and socket modules. BaseHandler.run calls the WSGI application callable which is any Python callable. self._write calls sys.stdout.buffer.write() in BaseCGIHandler, using gopy's file object.