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Groups > comp.lang.python > #72328
| References | <a7dbde77-6bec-4b04-a940-5e8beb926232@googlegroups.com> |
|---|---|
| From | Ian Kelly <ian.g.kelly@gmail.com> |
| Date | 2014-05-30 21:54 -0600 |
| Subject | Re: Yet another "simple" headscratcher |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.10504.1401508949.18130.python-list@python.org> (permalink) |
On Fri, May 30, 2014 at 9:38 PM, Josh English <Joshua.R.English@gmail.com> wrote: > I am trying to whip up a quick matrix class that can handle multiplication. > > Should be no problem, except when it fails. > > [SNIP] > > def zero_matrix(rows, cols): > row = [0] * cols > data = [] > for r in range(rows): > data.append(row) Each row of the matrix that you create here is the *same* list, not different lists that happen to be equal. So when you mutate one row, you mutate all of them. See: https://docs.python.org/3/faq/programming.html#how-do-i-create-a-multidimensional-list
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Yet another "simple" headscratcher Josh English <Joshua.R.English@gmail.com> - 2014-05-30 20:38 -0700
Re: Yet another "simple" headscratcher Josh English <Joshua.R.English@gmail.com> - 2014-05-30 20:55 -0700
Re: Yet another "simple" headscratcher Gary Herron <gary.herron@islandtraining.com> - 2014-05-30 20:57 -0700
Re: Yet another "simple" headscratcher Ian Kelly <ian.g.kelly@gmail.com> - 2014-05-30 21:54 -0600
Re: Yet another "simple" headscratcher wxjmfauth@gmail.com - 2014-05-30 23:46 -0700
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