[issue13557] exec of list comprehension fails on NameError
Roundup Robot devn...@psf.upfronthosting.co.za added the comment: New changeset ab22ffa6fb2e by Terry Jan Reedy in branch '2.7': Issue #13557: Clarify effect of giving two different namespaces to exec or http://hg.python.org/cpython/rev/ab22ffa6fb2e New changeset ea670d71a36d by Terry Jan Reedy in branch '3.2': Issue #13557: Clarify effect of giving two different namespaces to exec or http://hg.python.org/cpython/rev/ea670d71a36d New changeset b47ae7a9e685 by Terry Jan Reedy in branch 'default': Merge 3.2 closes issue 13557 http://hg.python.org/cpython/rev/b47ae7a9e685 -- nosy: +python-dev resolution: - fixed stage: needs patch - committed/rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13557] exec of list comprehension fails on NameError
Changes by Florent Xicluna florent.xicl...@gmail.com: -- nosy: +Trundle, anikom15, daniel.urban, flox, jonathan.hartley, josmiley, michael.foord, mjs0, rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13557] exec of list comprehension fails on NameError
Florent Xicluna florent.xicl...@gmail.com added the comment: Issue #11796 marked as duplicate of this one. However the issue described in #11796 does not involve exec/execfile. It is about scopes for list comprehension like this one. Another doc patch should probably be written to cover the case described in #11796 too. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13557] exec of list comprehension fails on NameError
Terry J. Reedy tjre...@udel.edu added the comment:
Issues like this, about exec, have come up multiple times. I just closed #14049
as a duplicate of this, and listed there some other issues. So I think that the
doc for exec (and execfile in 2.7) could be better still. I would like to see
something like the following added, whether instead of or in addition to the
current proposal -- perhaps after If provided, locals can be any mapping
object. (quote from the 3.2 exec entry)
At module level, globals and locals are the same dictionary. If one passes two
separate objects as globals and locals, the code will be executed as if it were
embedded in a class definition.
To me, this is friendlier and less intimidating than 'free variable' and the
Execution model doc chapter. It summarizes the essential problem with such exec
calls.
To illustrate, the following gives the same NameError. and for the same reason,
as exec(code,{},{}), where code is the quoted unindented version with the class
line deleted.
class x:
x = 1
def incx():
return x+1
print(incx())
--
nosy: +terry.reedy
versions: +Python 2.7, Python 3.2
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[issue13557] exec of list comprehension fails on NameError
Éric Araujo mer...@netwok.org added the comment: Stefan: This fell off my radar, sorry I haven’t reviewed your patch yet. Terry: +1 -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13557] exec of list comprehension fails on NameError
Stephan R.A. Deibel sdei...@wingware.com added the comment: Here's a patch to the docs that notes the issue and refers the reader to the relevant execution model docs page. I have also attempted to clarify the interaction with dynamic features section of the execution model page. -- keywords: +patch versions: -Python 2.7, Python 3.2 Added file: http://bugs.python.org/file23937/exec-eval-clarification.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13557] exec of list comprehension fails on NameError
Éric Araujo mer...@netwok.org added the comment: Would you like to make a doc patch? -- assignee: - docs@python components: +Documentation keywords: +easy nosy: +docs@python, eric.araujo resolution: invalid - stage: - needs patch versions: +Python 2.7, Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13557] exec of list comprehension fails on NameError
Amaury Forgeot d'Arc amaur...@gmail.com added the comment: This is expected and documented: http://docs.python.org/py3k/reference/executionmodel.html#interaction-with-dynamic-features Free variables are not resolved in the nearest enclosing namespace, but in the global namespace., a free variable being a variable used in a code block but not defined there. And yes, a list comprehension defines a code block. Try using exec(code, locals()). It's a good habit anyway to always pass a namespace to exec(). -- nosy: +amaury.forgeotdarc resolution: - invalid status: open - pending ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13557] exec of list comprehension fails on NameError
Stephan R.A. Deibel sdei...@wingware.com added the comment: Ah, thanks, there it is... I thought this must be dealt with somewhere but couldn't find it. Maybe should add something to the 'exec' statement docs http://docs.python.org/py3k/library/functions.html#exec to reference this (from a usability-of-docs standpoint). BTW, my code already sends the namespaces to exec (from current stack frame; it's part of a debugger) and probably would break other cases to alter this. Well, anyway, sorry for the invalid bug report... -- status: pending - open ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue13557] exec of list comprehension fails on NameError
New submission from Stephan R.A. Deibel sdei...@wingware.com: Calling exec() on code that includes a list comprehension that references a defined local variable x fails incorrectly on NameError: global name 'x' not defined. -- files: execlistcomp.py messages: 149050 nosy: sdeibel priority: normal severity: normal status: open title: exec of list comprehension fails on NameError type: behavior versions: Python 3.2 Added file: http://bugs.python.org/file23883/execlistcomp.py ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue13557 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
