Issue #15064: Use with-blocks for some examples in docs.

Doc/library/multiprocessing.rst

@@ -241,8 +241,7 @@ However, if you really do need to use some shared data then
           l.reverse()
 
       if __name__ == '__main__':
-          manager = Manager()
-
+          with Manager() as manager:
               d = manager.dict()
               l = manager.list(range(10))
 
@@ -279,7 +278,7 @@ For example::
        return x*x
 
    if __name__ == '__main__':
-       pool = Pool(processes=4)               # start 4 worker processes
+       with Pool(processes=4) as pool         # start 4 worker processes
            result = pool.apply_async(f, [10]) # evaluate "f(10)" asynchronously
            print(result.get(timeout=1))       # prints "100" unless your computer is *very* slow
            print(pool.map(f, range(10)))      # prints "[0, 1, 4,..., 81]"
@@ -1426,8 +1425,7 @@ callables with the manager class.  For example::
    MyManager.register('Maths', MathsClass)
 
    if __name__ == '__main__':
-       manager = MyManager()
-       manager.start()
+       with MyManager() as manager:
            maths = manager.Maths()
            print(maths.add(4, 3))         # prints 7
            print(maths.mul(7, 8))         # prints 56
@@ -1798,8 +1796,7 @@ The following example demonstrates the use of a pool::
        return x*x
 
    if __name__ == '__main__':
-       pool = Pool(processes=4)              # start 4 worker processes
-
+       with Pool(processes=4) as pool:         # start 4 worker processes
            result = pool.apply_async(f, (10,)) # evaluate "f(10)" asynchronously
            print(result.get(timeout=1))        # prints "100" unless your computer is *very* slow
 
@@ -1984,9 +1981,9 @@ the client::
    from array import array
 
    address = ('localhost', 6000)     # family is deduced to be 'AF_INET'
-   listener = Listener(address, authkey=b'secret password')
 
-   conn = listener.accept()
+   with Listener(address, authkey=b'secret password') as listener:
+       with listener.accept() as conn:
            print('connection accepted from', listener.last_accepted)
 
            conn.send([2.25, None, 'junk', float])
@@ -1995,9 +1992,6 @@ the client::
 
            conn.send_bytes(array('i', [42, 1729]))
 
-   conn.close()
-   listener.close()
-
 The following code connects to the server and receives some data from the
 server::
 
@@ -2005,8 +1999,8 @@ server::
    from array import array
 
    address = ('localhost', 6000)
-   conn = Client(address, authkey=b'secret password')
 
+   with Client(address, authkey=b'secret password') as conn:
        print(conn.recv())                  # => [2.25, None, 'junk', float]
 
        print(conn.recv_bytes())            # => 'hello'
@@ -2015,8 +2009,6 @@ server::
        print(conn.recv_bytes_into(arr))    # => 8
        print(arr)                          # => array('i', [42, 1729, 0, 0, 0])
 
-   conn.close()
-
 The following code uses :func:`~multiprocessing.connection.wait` to
 wait for messages from multiple processes at once::