On 10/2/2010 8:02 PM, Steven D'Aprano wrote:
On Sun, 3 Oct 2010 01:17:39 am bob gailer wrote:
I ran dis on a for loop and the equivalent comprehension.
I was surprised to see almost identical code.
I had assumed (and now wish for) that a comprehension would be a
primitive written in C and thus much faster!
How could it be? A list comp is syntactic sugar. It needs to perform the
same steps as a for-loop, and call an arbitrary Python expression. It's
not like map() that takes a function object. Unless you had a separate
primitive for every imaginable Python expression -- which is
impossible -- list comps need to generate relatively similar code to
for-loops because they do relatively similar things.
Thank you. I needed that!
Besides, in recent versions of Python the speed of for-loops is quite
good. The bottleneck is rarely the loop itself, but the work you do in
the loop or the size of the loop.
--
Bob Gailer
919-636-4239
Chapel Hill NC
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