#25485: Add context manager support to Telnet class.

Patch by Stéphane Wirtel.

Doc/library/telnetlib.rst

@@ -43,6 +43,17 @@ Character), EL (Erase Line), GA (Go Ahead), SB (Subnegotiation Begin).
    :exc:`EOFError` when the end of the connection is read, because they can return
    an empty string for other reasons.  See the individual descriptions below.
 
+   A :class:`Telnet` object is a context manager and can be used in a
+   :keyword:`with` statement.  When the :keyword:`with` block ends, the
+   :meth:`close` method is called::
+
+       >>> from telnetlib import Telnet
+       >>> with Telnet('localhost', 23) as tn:
+       ...     tn.interact()
+       ...
+
+   .. versionchanged:: 3.6 Context manager support added
+
 
 .. seealso::
 

Doc/whatsnew/3.6.rst

@@ -125,6 +125,13 @@ Previously, names of properties and slots which were not yet created on
 an instance were excluded.  (Contributed by Martin Panter in :issue:`25590`.)
 
 
+telnetlib
+---------
+
+:class:`~telnetlib.Telnet` is now a context manager (contributed by
+Stéphane Wirtel in :issue:`25485`).
+
+
 urllib.robotparser
 ------------------
 

Lib/telnetlib.py

@@ -637,6 +637,12 @@ class Telnet:
             raise EOFError
         return (-1, None, text)
 
+    def __enter__(self):
+        return self
+
+    def __exit__(self, type, value, traceback):
+        self.close()
+
 
 def test():
     """Test program for telnetlib.
@@ -660,11 +666,10 @@ def test():
             port = int(portstr)
         except ValueError:
             port = socket.getservbyname(portstr, 'tcp')
-    tn = Telnet()
+    with Telnet() as tn:
-    tn.set_debuglevel(debuglevel)
+        tn.set_debuglevel(debuglevel)
-    tn.open(host, port, timeout=0.5)
+        tn.open(host, port, timeout=0.5)
-    tn.interact()
+        tn.interact()
-    tn.close()
 
 if __name__ == '__main__':
     test()

Lib/test/test_telnetlib.py

@@ -42,6 +42,11 @@ class GeneralTests(TestCase):
         telnet = telnetlib.Telnet(HOST, self.port)
         telnet.sock.close()
 
+    def testContextManager(self):
+        with telnetlib.Telnet(HOST, self.port) as tn:
+            self.assertIsNotNone(tn.get_socket())
+        self.assertIsNone(tn.get_socket())
+
     def testTimeoutDefault(self):
         self.assertTrue(socket.getdefaulttimeout() is None)
         socket.setdefaulttimeout(30)

Misc/NEWS

@@ -10,6 +10,8 @@ Release date: XXXX-XX-XX
 Core and Builtins
 -----------------
 
+- Issue #25485: telnetlib.Telnet is now a context manager.
+
 - Issue #24097: Fixed crash in object.__reduce__() if slot name is freed inside
   __getattr__.