On 26 Feb 2007 05:50:24 -0800, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > I do not have a clue what is happening in the code below. > > >>> a=[[2,4],[9,3]] > >>> b=a > >>> [map(list.sort,b)] > [[None, None]] > >>> b > [[2, 4], [3, 9]] > >>> a > [[2, 4], [3, 9]] > > I want to make a copy of matrix a and then make changes to the > matrices separately. I assume that I am missing a fundamental > concept. Any help would be appreciated. >
this: >>> b=a does not make a copy. It binds the name b to the same object that is bound to the name a. If you want a copy, ask for a copy. >>> a = [1,2] >>> import copy >>> b = copy.copy(a) #shallow copy >>> a.append(3) >>> a,b ([1, 2, 3], [1, 2]) >>> You may need to do something else depending on exactly what copy semantics you want, read the docs on the copy module. -- http://mail.python.org/mailman/listinfo/python-list
