SamplingWithReplacement.py

#
# Use random numbers to emulates the Sampling with Replacement.
#
# We can specify the number of balls in the bin with 40% red balls and 60% green balls.
# We select 10 balls from the bin and calculate the probability of the red 
# balls in the samples. 
#

import random

def sampleingWithReplacement (total, replaceTimes):

    balls = []

    red = int (total * 40 / 100)
    green = total - red
    for i in range (red):
        balls.append (1)

    for i in range (green):
        balls.append (0)    

    #print ("Display balls in the bin.")
    #print (balls)

    numberOfRed = 0
    for i in range (replaceTimes):

        random.shuffle (balls)
        sample = balls [0: 10]
        s = sum (sample)
        if s == 0 or s == 1:
            numberOfRed += 1

    p = numberOfRed / replaceTimes
    print ("There are %d balls in the bin. (%d red balls, %d green balls)" % (total, red, green))
    print ("Select %d balls from the bin with replacement.")
    print ("Times of replacement               = %d" % replaceTimes)
    print ("Number of red balls in the sample  = %d" % numberOfRed)
    print ("Probability                        = %f" % p)
    print ("")

if __name__ == '__main__':

    replaceTimes = 10000
    sampleingWithReplacement (100, replaceTimes) # total = 100, probability = 0.034800
    sampleingWithReplacement (1000, replaceTimes) # total = 1000, probability = 0.046900
    sampleingWithReplacement (10000, replaceTimes) # total = 10000, probability = 0.047300
    sampleingWithReplacement (100000, replaceTimes) # total = 100000, probability = 0.043800