On 09/07/2011 03:57 PM, Martin Rixham wrote:
Hi all
I would appreciate some help understanding something. Basically I am
confused by the following:
>>> a = [[0, 0], [0, 0]]
>>> b = list(a)
>>> b[0][0] = 1
>>> a
[[1, 0], [0, 0]]
I expected the last line to be
[[0, 0], [0, 0]]
I hope that's clear enough.
Martin
You were expecting the assignment to "b" to create a copy of the
original list, and it does, but the copy is only one level deep.
So a and b are different lists, but a[i] and b[i] are the same objects
for each i.
There is a "deepcopy" in the library which may do what you expect.
Gary Herron
--
Gary Herron, PhD.
Department of Computer Science
DigiPen Institute of Technology
(425) 895-4418
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http://mail.python.org/mailman/listinfo/python-list
