More realistic example for selectors.py.

Doc/library/selectors.rst

@@ -210,33 +210,40 @@ below:
       :func:`select.kqueue` object.
 
 
-Examples of selector usage::
+Examples
+--------
 
-   >>> import selectors
+Here is a simple echo server implementation::
-   >>> import socket
+
-   >>>
+   import selectors
-   >>> s = selectors.DefaultSelector()
+   import socket
-   >>> r, w = socket.socketpair()
+
-   >>>
+   sel = selectors.DefaultSelector()
-   >>> r.setblocking(False)
+
-   >>> w.setblocking(False)
+   def accept(sock, mask):
-   >>>
+       conn, addr = sock.accept()  # Should be ready
-   >>> s.register(r, selectors.EVENT_READ)
+       print('accepted', conn, 'from', addr)
-   SelectorKey(fileobj=<socket.socket fd=4, family=AddressFamily.AF_UNIX, type=2049, proto=0>, fd=4, events=1, data=None)
+       conn.setblocking(False)
-   >>> s.register(w, selectors.EVENT_WRITE)
+       sel.register(conn, selectors.EVENT_READ, read)
-   SelectorKey(fileobj=<socket.socket fd=5, family=AddressFamily.AF_UNIX, type=2049, proto=0>, fd=5, events=2, data=None)
+
-   >>>
+   def read(conn, mask):
-   >>> print(s.select())
+       data = conn.recv(1000)  # Should be ready
-   [(SelectorKey(fileobj=<socket.socket fd=5, family=AddressFamily.AF_UNIX, type=2049, proto=0>, fd=5, events=2, data=None), 2)]
+       if data:
-   >>>
+           print('echoing', repr(data), 'to', conn)
-   >>> for key, events in s.select():
+           conn.send(data)  # Hope it won't block
-   ...     if events & selectors.EVENT_WRITE:
+       else:
-   ...         key.fileobj.send(b'spam')
+           print('closing', conn)
-   ...
+           sel.unregister(conn)
-   4
+           conn.close()
-   >>> for key, events in s.select():
+
-   ...     if events & selectors.EVENT_READ:
+   sock = socket.socket()
-   ...         print(key.fileobj.recv(1024))
+   sock.bind(('localhost', 1234))
-   ...
+   sock.listen(100)
-   b'spam'
+   sock.setblocking(False)
-   >>> s.close()
+   sel.register(sock, selectors.EVENT_READ, accept)
+
+   while True:
+       events = sel.select()
+       for key, mask in events:
+           callback = key.data
+           callback(key.fileobj, mask)