[Python-Dev] Don't set local variable in a list comprehension or generator

Nick Coghlan ncoghlan at gmail.com
Thu May 19 11:03:10 CEST 2011

On Thu, May 19, 2011 at 7:34 AM, Victor Stinner
<victor.stinner at haypocalc.com> wrote:
> But it is slower whereas I read somewhere than generators are faster
> than loops.

Are you sure it wasn't that generator expressions can be faster than
list comprehensions (if the memory savings are significant)?

Or that a reduction function with a generator expression can be faster
than a module-level explicit loop (due to the replacement of
dict-based variable assignment with fast locals in the generator and C
looping in the reduction function)?

In general, as long as both are using fast locals and looping in
Python, I would expect inline looping code to be faster than the
equivalent generator (but often harder to maintain due to lack of


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia

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