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According to the online documentation for threading
Lock objects, setting blocking=0 will produce a
non-blocking call.
But trying it in the command line causes the execution
to hang.
>>> import threading
>>> lock = threading.Lock()
>>> lock.acquire(blocking=0)
>>> lock.acquire(blocking=0)
[blocks]
----------------------------------
internal documentation claims that the keyword is wait,
but using wait produces the same problem:
>>> import threading
>>> lock = threading.Lock()
>>> lock.acquire.__doc__
'acquire([wait]) -> None or
Boolean\n(PyThread_acquire_lock() is an obsolete
synonym)\n\nLock the lock. Without argument, this
blocks if the lock is already\nlocked (even by the same
thread), waiting for another thread to release\nthe
lock, and return None when the lock is acquired.\nWith
a Boolean argument, this will only block if the
argument is true,\nand the return value reflects
whether the lock is acquired.\nThe blocking operation
is not interruptible.'
>>> lock.acquire(wait=0)
>>> lock.acquire(wait=0)
[blocks]
---------------------------------
Not using a keyword works fine:
>>> import threading
>>> lock = threading.Lock()
>>> lock.acquire(0)
1
>>> lock.acquire(0)
0
>>> 

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user_id=31435
Changed to docs and assigned to Fred for comment. Any idea 
how we can make this clearer? The docs don't claim this 
accepts a keyword argument, and lots of C functions simply 
ignore any keyword arguments that may be given.

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user_id=21627
This is fixed in Python 2.2; it will raise an exception
"acquire() takes no keyword arguments". That should make it
immediately clear how to read the documentation.

Logged In: YES 
user_id=31435
Thanks, Martin! Since this is already much better in 2.2, 
I'll take responsibility for closing it as Fixed.