Since threading is written in Python, one might expect Lock to be written in Python and its methods to accept keywords. However, threading.py (3.2) has
  _acquire_lock = _thread.acquire_lock
  Lock = _aquire_lock
so threading.Lock objects are C-coded _thread.lock objects and hence *might* not accept keyword args.

In 3.1:
lock.acquire([waitflag]) # same 2.7
Lock.acquire(blocking=True) # [blocking=1] in 2.7
Indeed the first is correct.

>>> from threading import Lock
>>> l=Lock()
>>> l.acquire(blocking=True)
Traceback (most recent call last):
  File "<pyshell#2>", line 1, in <module>
    l.acquire(blocking=True)
TypeError: acquire() takes no keyword arguments
>>> l.acquire(True)
True

r87596, r87596

In 3.2:
lock.acquire(waitflag=1, timeout=-1) 
Lock.acquire(blocking=True, timeout=-1)
The edit in 3.2 is actually correct 

>>> from threading import Lock
>>> l=Lock()
>>> l.acquire(blocking=True)
True
>>> l.acquire(timeout=1)
False

_thread.lock.acquire now accepts keywords.