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...) > > C:\>python -m timeit -s"from random import choice" "for x in range(10000): > " " choice([0, 1])" > 10 loops, best of 3: 22.8 msec per loop > > C:\>python -m timeit -s"from random import random" "for x in range(10000): > " " random()" > 1000 loops, best of 3: 1.84 msec per loop > > C:\>python -m timeit -s"from random import uniform" "for x in range(10000) > :" " uniform(0, 1)" > 100 loops, best of 3: 12.2 msec per loop > > C:\>python -m timeit -s"from random import randrange" "for x in range(1000 > 0):" " randrange(2)" > 10 loops, best of 3: 25.3 msec per loop > > C:\>python -m timeit -s"from random import randint" "for x in range(10000) > :" " randint(0, 1)" > 10 loops, best of 3: 45.9 msec per loop
Looking at the code and your numbers, my guess is that the time to make a Python function call on your computer is about 2 microseconds (20 msec / 10000). (I mean the entire overhead - looking up the function and actually calling it.) random.randint() just calls random.randrange() after incrementing the upper limit. So the difference in times between these two is one addition and a function call. randrange() does a little checking, then calls random(). The time difference is a little more than 20 msec, probably due to the argument checking. > Anyway, if you are making a coin flipping program, with a great many > flips and speed is important, it seems a good idea to avoid the > otherwise obvious choice of choice(). And more generally, in a highly optimized loop, avoid function calls if possible, they are relatively expensive in Python. Kent _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
