On 27Oct2009 14:01, Scott Pakin <scott+...@pakin.org> wrote: | copy.deepcopy apparently preserves multiple references to the same object: | | $ python | Python 2.5.2 (r252:60911, Jan 4 2009, 17:40:26) | [GCC 4.3.2] on linux2 | Type "help", "copyright", "credits" or "license" for more information. | >>> import copy | >>> d = [1,2,3] | >>> r = copy.deepcopy([d]*3) | >>> r | [[1, 2, 3], [1, 2, 3], [1, 2, 3]] | >>> r[1][2] = 999 | >>> d | [1, 2, 3] | >>> r | [[1, 2, 999], [1, 2, 999], [1, 2, 999]] | >>> | | I wanted to wind up with r being [[1, 2, 3], [1, 2, 999], [1, 2, 3]]. | What's the right way to construct r as a list of *independent* d lists?
Well, you would need to write your own. But consider this: x = [1, 2] x.append(x) Your deepercopy() function will explode. Probably the best method is to pre-munge the list you pass to deepcopy: d = [1,2,3] d3 = [d]*3 # pre-copy the multiple references d3deeper = [ list(d3i) for d3i in d3 ] r = copy.deepcopy(d3deeper) You can see this requires special knowledge of the structure you're copying though. -- Cameron Simpson <c...@zip.com.au> DoD#743 http://www.cskk.ezoshosting.com/cs/ The mere existence of a problem is no proof of the existence of a solution. - Yiddish Proverb -- http://mail.python.org/mailman/listinfo/python-list
