random_walk.py

import random

def random_walk(n):
    """Returns coordinates after 'n' block random walk."""
    x = 0
    y = 0
    for i in range(n):
        step = random.choice(['N', 'S', 'E', 'W'])
        if step == 'N':
            y = y + 1
        elif step == 'S':
            y = y - 1
        elif step == 'E':
            x = x + 1
        else:
            x = x - 1
    return(x, y)

def random_walk_2(n):
    """Returns the coordinates after n random walk."""
    x, y = 0, 0
    for i in range(n):
        (dx, dy) = random.choice([(0, 1), (0, -1), (1, 0), (-1, 0)])
        x += dx
        y += dy
    return (x, y)


# for i in range(25):
#     walk = random_walk_2(10)
#     print(walk, "distance from home",
#           abs(walk[0]) + abs(walk[1]))

# number_of_walks = 10000
number_of_walks = 20000

for walk_length in range(1, 31):
    no_transport = 0
    for i in range(number_of_walks):
        (x, y) = random_walk_2(walk_length)
        distance = abs(x) + abs(y)
        if distance <= 5:
            no_transport += 1
    no_transport_percentage = float(no_transport) / number_of_walks
    print("Walk size = ", walk_length,
    "/ % of no transport = ", 100 * no_transport_percentage)