#
# random walk problem, chapter 9 exercise 12
# in class
#
#  functions:
#
#    mean = average(list_of_numbers)
#
#    distance = random_walk(n_steps)
#
#

import random

def average(numbers):
    """ Return mean of a list of numbers. """
    return float(sum(numbers))/len(numbers)

def random_walk(n_steps):
    """ Return distance moved in random walk of n steps. """
    position = 0
    for i in range(n_steps):
        offset = random.choice([-1, 1])
        position = position + offset
    return position

def main():
    print "Finding average distance from random walk of n steps"
    n = input("What is n? ")
    iterations = 100
    distances = []
    for i in range(iterations):
        distances.append(random_walk(n))
    print "First few walks: %i, %i, %i" % \
        (distances[0], distances[1], distances[2])
    mean = average(distances)
    print "The mean of %i walks is %i" % (iterations, mean)

main()