[Python-Dev] Proposed addition to threading module - released

Mon Apr 24 05:44:52 CEST 2006

Do we want to add a "released" context manager to the threading module for 
2.5? It was mentioned using the name "unlocked" in PEP 343, but never spelt out:
class released(object):
 def __init__(self, lock):
 self.lock = lock
 def __enter__(self):
 self.lock.release()
 def __exit__(self, *exc_info):
 self.lock.acquire()
(This context manager is the equivalent of PEP 319's asynchronize keyword)
Usage would be:
 from threading import RLock, released
 sync_lock = RLock()
 def thread_safe():
 with sync_lock:
 # This is thread-safe
 with released(sync_lock):
 # Perform long-running or blocking operation
 # that doesn't need to hold the lock
 # We have the lock back here
(This particular example could be handled by two separate "with sync_lock" 
statements with the asynchronous operation between them, but other cases put 
the asynchronous operation inside a loop or a conditional statement which 
means that particular trick won't work).
Cheers,
Nick.
-- 
Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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