In Python 2.4.3 a Telnet.expect with timeout=0 would always make at least one call to Telnet.fill_rawq if a match couldn't be found and the connection was open.

In Python 2.7.1/2.7.3 Telnet.expect with timeout=0 breaks before any call to Telnet.fill_rawq if a match isn't found in already read raw/cooked data. Expected behavior is that on timeout=0 at least one non-blocking attempt should be made to read from the connection when necessary to fulfill a match.

From code inspection (including Python 2.7.3) timeout behavior was modified to provide an overall elapsed timeout instead of passing unmodified timeout to each select resulting in the failure.


Python 2.7.1 (r271:86832, Nov 27 2010, 18:30:46) [MSC v.1500 32 bit (Intel)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from telnetlib import Telnet
>>> import time
>>> tn = Telnet("scn.org", 23)
>>> time.sleep(5) # short wait for data to be available
>>> tn.expect(['.{16}'], 0)
(-1, None, '')
>>>

Python 2.4.3 (#69, Mar 29 2006, 17:35:34) [MSC v.1310 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from telnetlib import Telnet
>>> import time
>>> tn = Telnet("scn.org", 23)
>>> time.sleep(5) # short wait for data to be available
>>> tn.expect(['.{16}'], 0)
(0, <_sre.SRE_Match object at 0x01752410>, '\r\nSeattle Communit')
>>>