[Tutor] Why is random.choice so much slower than random.random()?

Luke Paireepinart rabidpoobear at gmail.com
Thu Oct 12 11:24:55 CEST 2006

Dick Moores wrote:
> Why is random.choice so much slower than random.random()? In fact, by 
> a factor of 12! And randint(). Some 25 times slower than random(). Why?
> (I know that random() is the basis for most of the other functions in 
> the random module, and a look at random.py, though I don't complete 
> understand it, gives me an idea what's going on with randint(), etc., still...)
I haven't looked at the random code, but what I expect is happening is that
for random.choice(a)
you need to
1) get a random number
2) convert that random number into an index into your list.  eg. [0,1] 
any random number < .5 would be index 0.
recall that random goes from 0 to 1.
3) grab that item from the list and return it.

I'm guessing that step 2 and step 3 are why it takes a while, since 
these are probably implemented in Python.

for random.randint(a,b):
It might do
so there's the overhead of generating the range.

Course this is completely speculation and may be not true at all, but I 
thought I'd give it a shot :)

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