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Re: Python Iterables struggling using map() built-in

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On Mon, Dec 8, 2014 at 11:12 AM, Roy Smith <roy@panix.com> wrote:
> Ugh.  When I see "while foo", my brain says, "OK, you're about to see a
> loop which is controlled by the value of foo being changed inside the
> loop".  That's not at all what's happening here, so my brain runs into a
> wall.

I agree, with the caveat that this kind of thing makes a fine infinite loop:

while "No exception raised":
    # do stuff that can raise an exception
while "Playing more games":
    play_game()
    if not still_playing: break
    reset_game_board()

Nobody expects a string literal to actually become false inside the
loop. With a local name, yes, I would expect it to at least have a
chance of becoming false.

> Next problem, what the heck is "res"?  We're not back in the punch-card
> days.  We don't have to abbreviate variable names to save columns.
> Variable names are supposed to describe what they hold, and thus help
> you understand the code.  I have no idea what "res" is supposed to be.
> Residue?  Result?  Rest_of_items?  Response?  None of these make much
> sense here, so I'm just left befuddled.

I take it as "result", which makes plenty of sense to me. It's the
thing that's about to be yielded. Given that there's not much else you
can say in a meta-function like zip(), I have no problem with that.
Here's a slightly different example:

def mark_last(it):
    it = iter(it)
    lastres = sentinel = object()
    while "more values coming":
        res = next(it, sentinel)
        if lastres is not sentinel: yield (lastres, res is sentinel)
        if res is sentinel: return
        lastres = res

Use of "res" for "result" and "lastres" to mean "res as of the
previous iteration of the loop" seems fine to me.

ChrisA

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Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-08 05:29 +1100
  Re: Python Iterables struggling using map() built-in Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-08 10:33 +1100
    Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-08 10:50 +1100
      Re: Python Iterables struggling using map() built-in Roy Smith <roy@panix.com> - 2014-12-07 19:27 -0500
        Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-08 11:35 +1100
          Re: Python Iterables struggling using map() built-in Steven D'Aprano <steve@pearwood.info> - 2014-12-08 09:40 +0000
            Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-08 20:50 +1100
            Re: Python Iterables struggling using map() built-in Roy Smith <roy@panix.com> - 2014-12-08 19:02 -0500
    Re: Python Iterables struggling using map() built-in Roy Smith <roy@panix.com> - 2014-12-07 19:12 -0500
      Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-08 11:34 +1100
        Re: Python Iterables struggling using map() built-in Roy Smith <roy@panix.com> - 2014-12-07 19:45 -0500
          Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-08 12:00 +1100
          Re: Python Iterables struggling using map() built-in MRAB <python@mrabarnett.plus.com> - 2014-12-08 03:09 +0000
      Re: Python Iterables struggling using map() built-in Terry Reedy <tjreedy@udel.edu> - 2014-12-07 19:38 -0500
        Re: Python Iterables struggling using map() built-in Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-12-08 18:06 +1300
      Re: Python Iterables struggling using map() built-in Ned Batchelder <ned@nedbatchelder.com> - 2014-12-07 20:06 -0500
      Re: Python Iterables struggling using map() built-in Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-09 13:50 +1100
        Re: Python Iterables struggling using map() built-in Terry Reedy <tjreedy@udel.edu> - 2014-12-09 00:03 -0500
          Re: Python Iterables struggling using map() built-in Steven D'Aprano <steve@pearwood.info> - 2014-12-09 06:40 +0000
        Re: Python Iterables struggling using map() built-in Terry Reedy <tjreedy@udel.edu> - 2014-12-09 15:06 -0500
          Re: Python Iterables struggling using map() built-in Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-10 11:10 +1100
            Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-10 11:20 +1100
            Re: Python Iterables struggling using map() built-in Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-12-10 00:24 +0000
            Re: Python Iterables struggling using map() built-in Roy Smith <roy@panix.com> - 2014-12-09 21:44 -0500
              Re: Python Iterables struggling using map() built-in Steven D'Aprano <steve@pearwood.info> - 2014-12-10 09:24 +0000
                Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-10 20:32 +1100
                Re: Python Iterables struggling using map() built-in Marko Rauhamaa <marko@pacujo.net> - 2014-12-10 12:58 +0200
                Re: Python Iterables struggling using map() built-in Ian Kelly <ian.g.kelly@gmail.com> - 2014-12-10 09:46 -0700
                Re: Python Iterables struggling using map() built-in Steven D'Aprano <steve@pearwood.info> - 2014-12-11 04:01 +0000
                Re: Python Iterables struggling using map() built-in Ian Kelly <ian.g.kelly@gmail.com> - 2014-12-11 15:00 -0700
                Re: Python Iterables struggling using map() built-in Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-12 10:28 +1100
                Re: Python Iterables struggling using map() built-in Ian Kelly <ian.g.kelly@gmail.com> - 2014-12-11 16:57 -0700
                Re: Python Iterables struggling using map() built-in Roy Smith <roy@panix.com> - 2014-12-11 20:55 -0500
                Re: Python Iterables struggling using map() built-in Ian Kelly <ian.g.kelly@gmail.com> - 2014-12-12 00:36 -0700
                Re: Python Iterables struggling using map() built-in Chris Angelico <rosuav@gmail.com> - 2014-12-12 11:44 +1100
                Re: Python Iterables struggling using map() built-in Terry Reedy <tjreedy@udel.edu> - 2014-12-10 12:48 -0500
                Re: Python Iterables struggling using map() built-in Ian Kelly <ian.g.kelly@gmail.com> - 2014-12-10 13:32 -0700
                Re: Python Iterables struggling using map() built-in Terry Reedy <tjreedy@udel.edu> - 2014-12-10 23:17 -0500
    Re: Python Iterables struggling using map() built-in Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-12-08 18:00 +1300

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