[Python-bugs-list] [ python-Bugs-510384 ] Separate Scope for List Comprehensions
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noreply@sourceforge.net
Wed, 30 Jan 2002 07:52:18 -0800
Bugs item #510384, was opened at 2002-01-29 14:13
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Category: Python Interpreter Core
Group: Feature Request
Status: Open
Resolution: None
Priority: 5
Submitted By: Raymond Hettinger (rhettinger)
Assigned to: Nobody/Anonymous (nobody)
Summary: Separate Scope for List Comprehensions
Initial Comment:
The variables in a list comprehension should not be in
the enclosing scope.
i=10
temp = [str(i) for i in range(5)]
print i
Should print 10 instead of 4.
Implement the above as:
i=10
def _listcomp():
for i in range(5):
yield str(i)
temp = list(_listcomp())
print i
Note, I timed the difference between the existing and
proposals implementations and found only a 4% decrease
in speed.
In case someone is already relying on the list
comprehension variables being in the local scope, a
deprecation warning or from __future__ in warranted.
Also note, this implementation leaves open the
possibility of creating generator comprehensions so
that temp=[yield str(i) for i in range(5)] creates the
same code as above except that the final 'list'
coercion is eliminated: temp=_listcomp
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Comment By: Nobody/Anonymous (nobody)
Date: 2002-01-30 07:52
Message:
Logged In: NO
This is Guido; I can't log in here on the road.
I believe this has been fixed in Python 2.2, and possibly
in 2.1.2. Can you check that?
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