Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #44215

Re: Nested iteration?

Show all headers | View raw

[Multipart message — attachments visible in raw view] - view raw

On 23 April 2013 21:49, Terry Jan Reedy <tjreedy@udel.edu> wrote:

> ri= iter(range(3))
> for i in ri:
>     for j in ri:
>         print(i,j)
> # this is somewhat deceptive as the outer loop executes just once
> 0 1
> 0 2
>
> I personally would add a 'break' after 'outer_line = next(f)', since the
> first loop is effectively done anyway at that point, and dedent the second
> for statement. I find to following clearer
>
> ri= iter(range(3))
> for i in ri:
>     break
> for j in ri:
>     print(i,j)
> # this makes it clear that the first loop executes just once
> 0 1
> 0 2
>
> I would only nest if the inner loop could terminate without exhausting the
> iterator and I wanted the outer loop to then resume.
>

Surely a normal programmer would think "next(ri, None)" rather than a loop
that just breaks.

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Nested iteration? roy@panix.com (Roy Smith) - 2013-04-23 11:40 -0400
  Re: Nested iteration? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-04-23 17:05 +0100
  Re: Nested iteration? Ian Kelly <ian.g.kelly@gmail.com> - 2013-04-23 10:05 -0600
  Re: Nested iteration? Peter Otten <__peter__@web.de> - 2013-04-23 18:15 +0200
  Re: Nested iteration? Chris Angelico <rosuav@gmail.com> - 2013-04-24 02:21 +1000
  Re: Nested iteration? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-23 16:35 +0000
  Re: Nested iteration? Ian Kelly <ian.g.kelly@gmail.com> - 2013-04-23 10:30 -0600
  Re: Nested iteration? Ian Kelly <ian.g.kelly@gmail.com> - 2013-04-23 10:39 -0600
  Re: Nested iteration? Chris Angelico <rosuav@gmail.com> - 2013-04-24 02:42 +1000
    Re: Nested iteration? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-23 16:53 +0000
  Re: Nested iteration? Terry Jan Reedy <tjreedy@udel.edu> - 2013-04-23 16:49 -0400
  Re: Nested iteration? Joshua Landau <joshua.landau.ws@gmail.com> - 2013-04-23 22:14 +0100
  Re: Nested iteration? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-04-23 22:29 +0100
  Re: Nested iteration? Joshua Landau <joshua.landau.ws@gmail.com> - 2013-04-23 22:41 +0100
  Re: Nested iteration? Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2013-04-23 23:42 +0100

csiph-web