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Groups > comp.lang.python > #92582
| Subject | Re: zip as iterator and bad/good practices |
|---|---|
| References | <mles66$sk2$1@speranza.aioe.org> |
| From | jimages <jimages123@gmail.com> |
| Date | 2015-06-13 13:32 +0800 |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.452.1434175078.13271.python-list@python.org> (permalink) |
> On Jun 12, 2015, at 11:00 PM, Fabien <fabien.maussion@gmail.com> wrote:
> but that awful bug made me wonder: is it a bad practice to interactively modify the list you are iterating over?
Yes.
I am a newbie. I also have been confused when I read the tutorial. It recommends make a copy before looping. Then I try.
#--------------------------
Test = [1, 2]
For i in Test:
Test.append(i)
#--------------------------
But when i execute. The script does not end. I know there must something wrong. So I launch debugger and deserve the list after each loop.
And I see:
Loop 1: [ 1, 2, 1]
Loop 2: [ 1, 2, 1, 2]
Loop 3: [ 1, 2, 1, 2, 1]
Loop 4: [ 1, 2, 1, 2, 1, 2]
......
So you can see that loop will *never* end.
So I think you regard the 'i' as a pointer. After execute one loop the pointer repoints to next element , but at the same time you are appending element. So pointer will *never* repoints to the last element.
How to solve?
Change code to this
#--------------------------
Test = [1, 2]
For i in Test[:] :
Test.append(i)
#--------------------------
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zip as iterator and bad/good practices Fabien <fabien.maussion@gmail.com> - 2015-06-12 17:00 +0200
Re: zip as iterator and bad/good practices Fabien <fabien.maussion@gmail.com> - 2015-06-12 17:05 +0200
Re: zip as iterator and bad/good practices Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-12 09:26 -0600
Re: zip as iterator and bad/good practices Fabien <fabien.maussion@gmail.com> - 2015-06-12 17:34 +0200
Re: zip as iterator and bad/good practices Fabien <fabien.maussion@gmail.com> - 2015-06-12 17:59 +0200
Re: zip as iterator and bad/good practices Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-12 17:22 +0100
Re: zip as iterator and bad/good practices Laura Creighton <lac@openend.se> - 2015-06-12 22:34 +0200
Re: zip as iterator and bad/good practices Terry Reedy <tjreedy@udel.edu> - 2015-06-12 19:27 -0400
Re: zip as iterator and bad/good practices Terry Reedy <tjreedy@udel.edu> - 2015-06-12 19:43 -0400
Re: zip as iterator and bad/good practices sohcahtoa82@gmail.com - 2015-06-12 17:02 -0700
Re: zip as iterator and bad/good practices Chris Angelico <rosuav@gmail.com> - 2015-06-13 10:26 +1000
Re: zip as iterator and bad/good practices sohcahtoa82@gmail.com - 2015-06-12 17:39 -0700
Re: zip as iterator and bad/good practices jimages <jimages123@gmail.com> - 2015-06-13 13:32 +0800
Re: zip as iterator and bad/good practices Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-06-13 07:17 +0000
Re: zip as iterator and bad/good practices Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2015-06-13 13:48 +0100
Re: zip as iterator and bad/good practices Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-06-13 16:16 +0000
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