Source

udacity373_code / unit1 / u1-21_inexact_motion.py

#Modify the move function to accommodate the added 
#probabilities of overshooting or undershooting 
#the intended destination.

p=[0, 1, 0, 0, 0]
world=['green', 'red', 'red', 'green', 'green']
measurements = ['red', 'green']
pHit = 0.6
pMiss = 0.2
pExact = 0.8
pOvershoot = 0.1
pUndershoot = 0.1

def sense(p, Z):
    q=[]
    for i in range(len(p)):
        hit = (Z == world[i])
        q.append(p[i] * (hit * pHit + (1-hit) * pMiss))
    s = sum(q)
    for i in range(len(q)):
        q[i] = q[i] / s
    return q

def move(p, U):
    q = [0.0 for i in p]
    for i in range(len(p)):
        q[(i+U-1)% len(p)] += p[i] * pUndershoot
        q[(i+U)% len(p)]   += p[i] * pExact
        q[(i+U+1)% len(p)] += p[i] * pOvershoot
    return q
    

print move(p, 1)