On Sun, 12 Feb 2006 06:01:55 -0800, [EMAIL PROTECTED] wrote: > I *think* Python uses reference counting for garbage collection.
Yes it does, with special code for detecting and collecting circular references. > I've > heard talk of people wanting to change this (to mark and sweep?). Reference counting is too simple to be cool *wink* [snip] > Make sure you are not creating > a circular reference. Something like this: > > a = [1, 2, 3, 4, 5, 6] > b = ['a', 'b', 'c', 'd'] > c = [10, 20, 30, 40] > > a[3] = b > b[1] = c > c[0] = a > > the last assignment creates a circular refence, and until it is removed, > non of these objects will be removed from memory. I believe Python now handles this sort of situation very well now. > I'm not an expert on python internals, and it is possible that they have > a way of checking for cases like this. I think the deepcopy method > catches this, but I don't *think* basic garbage collection look for this > sort of thing. deepcopy has nothing to do with garbage collection. This is where you use deepcopy: py> a = [2, 4, [0, 1, 2], 8] # note the nested list py> b = a # b and a both are bound to the same list py> b is a # b is the same list as a, not just a copy True py> c = a[:] # make a shallow copy of a py> c is a # c is a copy of a, not a itself False py> c[2] is a[2] # but both a and c include the same nested list True What if you want c to include a copy of the nested list? That's where you use deepcopy: py> d = copy.deepcopy(a) py> d[2] is a[2] False -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
