[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.
The concept you are missing is the fact that b = a makes b another name
for your nested list. As you correctly stated you really want a copy.
This will do what you want:
>>> import copy
>>> a=[[2,4],[9,3]]
>>> b = copy.deepcopy(a)
>>> [map(list.sort,b)]
[[None, None]]
>>> a
[[2, 4], [9, 3]]
>>> b
[[2, 4], [3, 9]]
cu
Philipp
--
Dr. Philipp Pagel Tel. +49-8161-71 2131
Dept. of Genome Oriented Bioinformatics Fax. +49-8161-71 2186
Technical University of Munich
http://mips.gsf.de/staff/pagel
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