micropython-lib/random/random.py

from urandom import *


def randrange(start, stop=None):
    if stop is None:
        stop = start
        start = 0
    upper = stop - start
    bits = 0
    pwr2 = 1
    while upper > pwr2:
        pwr2 <<= 1
        bits += 1
    while True:
        r = getrandbits(bits)
        if r < upper:
            break
    return r + start
random: Add randrange() implementation. The idea behind this implementation is that getrandbits() is guaranteed (required) to be equally distributed. Thus, we can just repeatedly sample it until get a suitable value, there's no bias accumulated and the process should be finite (and on average take few iterations). 2017-11-25 10:30:42 +00:00			`from urandom import *`


			`def randrange(start, stop=None):`
			`if stop is None:`
			`stop = start`
			`start = 0`
			`upper = stop - start`
			`bits = 0`
			`pwr2 = 1`
			`while upper > pwr2:`
			`pwr2 <<= 1`
			`bits += 1`
			`while True:`
			`r = getrandbits(bits)`
			`if r < upper:`
			`break`
			`return r + start`