[Patches] [ python-Patches-1492509 ] Unification of list-comp and for syntax

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Patches item #1492509, was opened at 2006-05-21 11:06
Message generated for change (Comment added) made by jimjjewett
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Category: Core (C code)
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Submitted By: Heiko Wundram (hwundram)
Assigned to: Nobody/Anonymous (nobody)
Summary: Unification of list-comp and for syntax

Initial Comment:
The following patch adds the ability for:

for <expr> in <expr> if <expr>:
    <do something>

to the Python core. This unifies the syntax of
list/generator comprehensions and the for statement
somewhat, because both now accept conditions which
produce an immediate continue.

I've posted a PEP to python-dev, which details the
changes this patch makes (which are all
backwards-compatible).

The patch doesn't try to address more than the actual
code required to make this feature work yet (except for
changes to Modules/parsermodule.c and Doc/ref/ref7.tex,
which details the for statement). If there's consensus
on this feature, I'll gladly produce more documentation.

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Comment By: Jim Jewett (jimjjewett)
Date: 2006-05-23 15:53

Message:
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I'm not loving the interaction with conditional expressions.

for x in (1,2,3) if test else (3,2,1):

I suppose this techically isn't ambiguous because else is a 
keyword.

On the other hand, you could do it now using he if-else

for x in real_seq if test else ():



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