random.randint() slow, esp in Python 3

Chris Angelico rosuav at gmail.com
Sat Sep 24 14:33:50 CEST 2011


On Sat, Sep 24, 2011 at 4:55 PM, Steven D'Aprano
<steve+comp.lang.python at pearwood.info> wrote:
> Chris Angelico wrote:
>
> If you want unbiased, random (or at least pseudo-random) integers chosen
> from an uniform distribution with proper error checking, you should use
> randint or randrange.
>
> "I only need random-ish ints, but I need 'em yesterday!!!"

All I want is some data to sort, so that I can verify that my
implementation is doing the same thing in every language that I write
it in. Doesn't have to be casino-level purity of randomness.

> You can't measure the speed of:
>
> [random.randint(0,sz*10-1) for i in range(sz)]
>
> and draw conclusions about randint alone.

Sure, but by comparing the two lines of code (one with randint and one
with random()), the other aspects can be cancelled out.

> For what (little) it's worth, it seems that Python 3.2 should be a bit
> faster than 2.6, at least if you consider the Pystone benchmark to mean
> anything.
>
> http://www.levigross.com/post/2340736877/pystone-benchmark-on-2-6-2-7-3-2

That's what I would normally expect, that the new version outperforms
the old - regardless of the program and the context. Exceptions need
justification (as in the case of int/long vs just int - Py2 often
outperforms Py3 when all the numbers fit inside machine int).

> You do know that Python's heap implementation is written in C? Don't be
> fooled by the heapq module being in Python.

I didn't know, but it doesn't surprise me. But my purpose wasn't to
sort the integers, it was to play with a particular hand-rolled
implementation of a heap sort in multiple languages and make sure it
was producing consistent results.

ChrisA



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