[Python-3000] threading, part 2 (original) (raw)

Josiah Carlson jcarlson at uci.edu
Fri Aug 11 17:45:54 CEST 2006

Slawomir Nowaczyk <slawomir.nowaczyk.847 at student.lu.se> wrote:

I believe that if asynchronous exception raising ever gets officially approved, there absolutely needs to be a way to block it for a piece of code that should execute atomically.

There is already a way of making Python source execution atomic with respect to other Python code [1].

But it should not be done lightly and never when the code is not specifically expecting it.

If you don't want random exceptions being raised in your threads, then don't use this method that is capable of raising exceptions somewhat randomly.

[1] Remove the two sys.setcheckinterval calls to verify this works. "proper" use should probably use try/finally wrapping.

import sys import threading import time

x = 0

def thr(n): ... global x ... while not x: ... time.sleep(.01) ... for i in xrange(n): ... sys.setcheckinterval(sys.maxint) ... _x = x + 1 ... x, _x = _x, x ... sys.setcheckinterval(100) ... for i in xrange(10): ... threading.Thread(target=thr, args=(1000000,)).start() ... x += 1 while threading.activeCount() > 1: ... time.sleep(.1) ... print x 10000001

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