On 06/06/2018 03:51 PM, Nick Coghlan wrote: > On 6 June 2018 at 15:31, Rob Cliffe via Python-Dev <python-dev@python.org <mailto:python-dev@python.org>> wrote: > ... > *In other words, it looks as if in Python 3.6.5, the compiled list comprehension** > **can "see" a pre-existing global variable but not a local one.* > > Yes, this is expected behaviour - the two-namespace form of exec (which is what you get implicitly when you use it inside a function body) is similar to a class body, and hence nested functions > (including the implicit ones created for comprehensions) can't see the top level local variables.
In issue 13557 [1] Amaury gives the following explanation by quoting the documentation [2] "Free variables are not resolved in the nearest enclosing namespace, but in the global namespace" and hints at the same solution that is proposed by Nick.
FWIW in issue 21161 [3] folks have been bitten by this when trying to run a list comprehension in pdb. [1] https://bugs.python.org/issue13557 [2] http://docs.python.org/py3k/reference/executionmodel.html#interaction-with-dynamic-features [3] https://bugs.python.org/issue21161 Xavier _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
