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[Python-Dev] listcomps vs. for loops

Guido van Rossum guido at python.org
Tue Oct 21 19:27:28 EDT 2003 
> >     for x in R:
> >         ...
> >     print x
> 
> For which reason I propose that Python 3.0 have the control name in
> any for expression be "local" to the expression ;)

What expression?

If you're talking about making

  x = None
  for x in R: pass
  print x # last item of R

illegal, forget it.  That's too darn useful.

> Hmm - actually this does raise another issue.
> 
>     >>> x = 1
>     >>> y = [1, 2, 3]
>     >>> y = [x for x in y]
> 
> Using the current semantics:
> 
>     >>> print x
>     3
> 
> Using the new semantics:
> 
>     >>> print x
>     1
> 
> Is this a problem? Are the new semantics going to cause confusion?

No, and no; we already went over this (but I don't blame you for not
reading every msg in this thread :-).  It does mean that we have to
start issuing proper deprecation warnings, and maybe we won't be able
to properly fix the LC scope thing before 3.0.

--Guido van Rossum (home page: http://www.python.org/~guido/)
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