J Kenneth King <[EMAIL PROTECTED]> writes: > I recently encountered some interesting behaviour that looks like a bug > to me, but I can't find the appropriate reference to any specifications > to clarify whether it is a bug. > > Here's the example code to demonstrate the issue: > > class SomeObject(object): > > def __init__(self): > self.words = ['one', 'two', 'three', 'four', 'five'] > > def main(self): > recursive_func(self.words) > print self.words > > def recursive_func(words): > if len(words) > 0: > word = words.pop() > print "Popped: %s" % word > recursive_func(words) > else: > print "Done" > > if __name__ == '__main__': > weird_obj = SomeObject() > weird_obj.main() > > > The output is: > > Popped: five > Popped: four > Popped: three > Popped: two > Popped: one > Done > [] > > Of course I expected that recursive_func() would receive a copy of > weird_obj.words but it appears to happily modify the object. > > Of course a work around is to explicitly create a copy of the object > property befor passing it to recursive_func, but if it's used more than > once inside various parts of the class that could get messy. > > Any thoughts? Am I crazy and this is supposed to be the way python works?
That's because Python isn't call-by-value. Or it is according to some, it's just that the values it passes are references. Which, according to others, is unnecessarily convoluted: it's call-by-object, or shall we call it call-by-sharing? At least everybody agrees it's not call-by-reference or call-by-name. There. I hope this helps! -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list
