[Python-Dev] Tricky way of of creating a generator via a comprehension expression

Paul Moore p.f.moore at gmail.com
Thu Nov 23 09:30:54 EST 2017

On 23 November 2017 at 14:24, Ivan Levkivskyi <levkivskyi at gmail.com> wrote:
>> My main concern is that comprehension is not equivalent to a for loop
>> for a specific reason - the scope issue. Has anyone looked back at the
>> original discussions to confirm *why* a function was used?
>> My recollection:
>> >>> i = 1
>> >>> a = [i for i in (1,2,3)]
>> >>> print(i)
>> 1
>> Serihy's approach (and your described expansion) would have print(i)
>> return NameError.
> Absolutely no, it will still print 1. The internal implementation will use
> unique ids internally (see https://bugs.python.org/issue10544 for details).

Ok, cool. My main point still applies though - has anyone confirmed
why a function scope was considered necessary at the time of the
original implementation, but it's apparently not now? I'm pretty sure
it was a deliberate choice, not an accident.


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