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Date: Wed, 12 Aug 2015 19:14:30 +1000
Subject: Re: Ensure unwanted names removed in class definition
From: Chris Angelico <rosuav@gmail.com>
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Xref: csiph.com comp.lang.python:95276

On Wed, Aug 12, 2015 at 7:01 PM, Ben Finney <ben+python@benfinney.id.au> wr=
ote:
>     class Parrot:
>         """ A parrot with beautiful plumage. """
>
>         plumage =3D [
>                 (foo, bar) for (foo, bar) in feathers.items()
>                 if bar =3D=3D "beautiful"]
>         del foo, bar  # =E2=86=90 FAILS, =E2=80=9CNameError: name 'foo' i=
s not defined=E2=80=9D
>
> How can I write the class definition with the list comprehension and
> *not* keep the incidental names =E2=80=94 in code that will run correctly=
 on
> both Python 2 and Python 3?

You could always do explicitly what a Py3 comprehension does, and wrap
it in a function:

plumage =3D (lambda: [
    (foo, bar) for (foo, bar) in feathers.items()
    if bar =3D=3D "beautiful"])()

Hardly clean code, but it will work, and apart from having a redundant
layer of protection in Py3, will do exactly the same thing on both. Is
the lambda nesting cruft worth it?

ChrisA