[Tutor] List comprehension question

[Albert-Jan Roskam]

For larger blocks of code, cProfile may also be useful for speed tests.

 Cheers!!
Albert-Jan


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________________________________
From: Steven D'Aprano <steve at pearwood.info>
To: tutor at python.org
Sent: Tue, November 9, 2010 9:54:24 PM
Subject: Re: [Tutor] List comprehension question

Richard D. Moores wrote:

> See <http://tutoree7.pastebin.com/R82876Eg> for a speed test with n =
> 100,000 and 100,000 loops

As a general rule, you shouldn't try to roll your own speed tests. There are 
various subtleties that can throw your results right out. Timing small code 
snippets on modern multi-tasking computers is fraught with difficulties.

Fortunately Python comes with that battery already included: the timeit module. 
You can use it from the shell like this:

python -m timeit -s "setup code goes here" "test code goes here"

At the Python interactive interpreter, the most useful pattern I've found is:

from timeit import Timer
t = Timer("proper_divisors(n)",
    "from __main__ import proper_divisors; n = 100000")
min(t.repeat(repeat=5, number=100000))


Or if you're happy with Python's defaults, that last line can be just:

min(t.repeat())



-- Steven
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