on Generators vs. List Comprehensions

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Author: Andy Sy
Date:  
To: python
Subject: on Generators vs. List Comprehensions
I love list comprehensions and took to them like a duck to
water, however, I have difficulty appreciating generators
to this day.

It's interesting however how generators are supposed to be
analogous to list comprehensions in roughly the same way
xrange() is to range().

I certainly found the posts here

http://www.amber.org/~petrilli/archive/2003/11/05/pythons_growing_complexity.html

very illuminating and will be revisiting generators armed
with a new perspecttive.


Another possible benefit of generators - PERFORMANCE - accdg.
to David Mertz in http://www-106.ibm.com/developerworks/library/l-pygen.html

"In Python, function invocation is rather expensive; among other
factors, function arguments lists take a while to sort out (positional
and default arguments need to be parsed, among other things). Also,
initializing a frame object takes some setup steps (over 100 lines
of C, according to Tim Peters on comp.lang.python; I have not examined
the Python source myself). Resuming a generator, in contrast, is
quite cheap; the arguments have already been parsed, and the frame
object is just sitting around waiting for resumption (almost no extra
initialization is needed)."

Hmmm......



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