Interacting with python

stonepaperscissor.py

import random
def mainfunction():
 while True:
    rnum = random.randrange(1,4)
    cpuschoice = numtochoice(rnum)
    userscoice = input("Choose between stone, paper and scissor\n")
    print('Cpu has choosen : ', cpuschoice)
    print(decision(userscoice.lower(), cpuschoice))

def numtochoice(num):
    switcher = {
     1:'stone',
     2:'paper',
     3:'scissor'
    }
    return switcher.get(num)

def decision(user, cpu):
    result = 'you lose'
    if cpu=='stone' :
        if user=='paper' :
            result = 'you win'
    elif cpu=='paper' :
        if user=='scissor' :
            result= 'you win'
    elif cpu == 'scissor' :
        if user == 'stone' :
            result = 'you win'
    if cpu == user :
        result = 'it was a draw'
    return result

mainfunction()