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Automatic thread safety for classes

P: n/a

Another useful code snippet...

This allows you to take a non-threadsafe class, and
automatically generate a threadsafe class. When a
method is called for your class, it automatically
locks the object, then calls the method, then unlocks
the object. You will have to perform any further
locking/unlocking manually.

# -------------------------------------------------
# threadclass: Get a threadsafe copy of a class.
# -------------------------------------------------

import types, threading
def threadclass(C):
"""Returns a 'threadsafe' copy of class C.
All public methods are modified to lock the
object when called."""
class D(C):
def __init__(self):
self.lock = threading.RLock()
C.__init__(self)

def ubthreadfunction(f):
def g(self, *args, **kwargs):
self.lock.acquire()
ans = f(self, *args, **kwargs)
self.lock.release()
return ans
return g

for a in dir(D):
f = getattr(D, a)
if isinstance(f, types.UnboundMethodType) and
a[:2] != '__':
setattr(D, a, ubthreadfunction(f))
return D
Example:

class Counter:
def __init__(self):
self.val = 0
def increment(self):
self.val += 1

SafeCounter = threadclass(Counter)
Now SafeCounter is a threadsafe class. Try it out!

Enjoy,
Connelly Barnes

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Jul 18 '05 #1
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1 Reply


P: n/a
To properly handle exceptions, the code in the previous posting should
be modified to include a try...finally block:

def ubthreadfunction(f):
def g(self, *args, **kwargs):
try:
self.lock.acquire()
ans = f(self, *args, **kwargs)
finally:
self.lock.release()
return ans
return g

- Connelly
Jul 18 '05 #2

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