Steven Bethard wrote:
Robert Kern wrote:
Mike Meyer wrote:
Ok, we've added list comprehensions to the language, and seen that
they were good. We've added generator expressions to the language, and
seen that they were good as well.
I'm left a bit confused, though - when would I use a list comp instead
of a generator expression if I'm going to require 2.4 anyway?
Never. If you really need a list
list(x*x for x in xrange(10))
Not quite true. If you discovered the unlikely scenario that the
construction of a list from the generator expression was an efficiency
bottleneck, you might choose a list comprehension -- they're slightly
faster when you really do want a list:
$ python -m timeit "list(x*x for x in xrange(10))"
100000 loops, best of 3: 6.54 usec per loop
$ python -m timeit "[x*x for x in xrange(10)]"
100000 loops, best of 3: 5.08 usec per loop
Okay, okay, *almost* never.
However, I don't expect that speed relationship to hold past Python 2.4.
--
Robert Kern
[EMAIL PROTECTED]
"In the fields of hell where the grass grows high
Are the graves of dreams allowed to die."
-- Richard Harter
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