On 9 May 2010, at 16:29, Xavier Ho wrote:
On Sun, May 9, 2010 at 6:20 PM, gopi krishna
<[email protected]<mailto:[email protected]>> wrote:
Why list comprehension faster than for loop?
Because Python optimises for certain special cases, when the number of
iterations is predicable in a list comprehension.
The fact that list comprehensions can only be comprised of expressions, not
statements, is a considerable factor, as much less work is required behind the
scenes for each iteration. Another factor is that the underlying iteration
mechanism for list comprehensions is much closer to a C loop than execution of
a for loop. Exact same reason Perl's map { } is much faster than an equivalent
for/foreach loop. (Psyco can speed up certain list comprehensions quite
significantly, too, but it isn't able to perform the same magic on an
equivalent for loop.)
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