distributions.py

import random
import math

def rand7():
    return random.randrange(1,8)

def rand5_mod():
    return rand7() % 5 + 1

def rand5_recursive():
    roll = rand7()
    return roll if roll <= 5 else rand5_recursive()

def rand5_while():
    result = 7 # arbitrarily large
    while result > 5:
        result = rand7()
    return result

def rand5_scale():
    return int(math.ceil((rand7() / 7.0) * 5.0))

def test_distributions():
    appearances = [0] * 10
    for time in range(1000000):
        result = rand5_mod()
        appearances[result] += 1

    print "rand5_mod"
    print appearances

    appearances = [0] * 10
    for time in range(1000000):
        result = rand5_recursive()
        appearances[result] += 1

    print "rand5_recursive"
    print appearances

    appearances = [0] * 10
    for time in range(1000000):
        result = rand5_while()
        appearances[result] += 1

    print "rand5_while"
    print appearances

    appearances = [0] * 10
    for time in range(1000000):
        result = rand5_scale()
        appearances[result] += 1

    print "rand5_scale"
    print appearances