Rock, Paper, Scissors... can't seem to get it to work properly

Question

I am having a bit of a problem with my rock, paper, scissors game. I'm trying to make the for loop work but when there's a tie, it won't print what I wrote.

import random
#main function
def main():
    for game_count in range(5):
        answer = int(input("Enter 1 for Rock, 2 for Paper, 3 for Scissors: "))
        number = random.randrange(1,4)
        if answer == 1:
            position = "rock"
            print("You choose", position)
        elif answer == 2:
            position = "paper"
            print("You choose", position)
        elif answer == 3:
            position = "scissors"
            print("You choose", position)
        else:
            print("pick either 1, 2, or 3")
            return main()
#computer picks what to play    
        if number == 1:
            print("Computer chooses Rock")
        elif number == 2:
            print("Computer chooses Paper")
        elif number == 3:
            print("Computer chooses Paper")
        return number
#if there is a tie
        if answer == number:
            print("It's a tie. Go again")
main()

After you `return number`, the function is finished - the last two lines never run. — jonrsharpe, Oct 26 '14 at 09:36
It's a bad idea, to recursively call `main` if you only want to repeat the input. — Daniel, Oct 26 '14 at 09:45
On that note, you may find http://stackoverflow.com/q/23294658/3001761 useful — jonrsharpe, Oct 26 '14 at 09:49
This code highlights one of the *nastiest* things about Python. Van Rossum still had half of his life to live when he designed Python, and thought that `elif` would change the lives of all the people who had been typing `elsif`, `elseif`, `else if`, and even `else { if` all of their lives. The problem was that his was the wind that blew no one any good. I hope he's regretting it now as much as the rest of the world is. — Borodin, Oct 26 '14 at 19:25

score 1 · Answer 1 · answered Oct 26 '14 at 10:15

It's unnecessary to write a main function, and it's certainly a bad idea to call it recursively to form a loop.

This program may interest you.

from random import randrange
from string import capitalize

weapons = [ 'rock',   'paper', 'scissors' ]
actions = [ 'blunts', 'wraps', 'cuts' ]

games = 0

while True:

    answer, position = None, None

    while True:
        answer = int(input("\nEnter 1 for Rock, 2 for Paper, 3 for Scissors: "))
        answer -= 1
        position = weapons[answer]
        if position:
            break
        print("Pick either 1, 2, or 3")

    print("You choose %s" % position)

    number = randrange(3)
    cpos = weapons[number]
    print("Computer chooses %s" % cpos)

    outcome = (answer - number) % 3

    if outcome == 0:
        print("It's a tie. Go again")
    elif outcome == 1:
        print(capitalize("%s %s %s" % (position, actions[answer], cpos)))
        print("Congratulations, you win!")
    elif outcome == 2:
        print(capitalize("%s %s %s" % (cpos, actions[number], position)))
        print("Computer wins!")

    games += 1
    if games == 5:
        break

print("Thanks for playing")

I'm puzzled here, I do like this implementation (would `+1`) but on the other hand it seems to me that user is "*implementing his homework*" and it doesn't provide any explanation why are pieces of his code ... "*useless*" and why stuff should be done differently (would `-1`). — Vyktor, Oct 26 '14 at 10:43
@Vyktor: I agree with what you're saying. Since the problem has already been answered in the comments, my intention was to make a couple of relevant points and provide something the OP may find useful as a source of ideas. It is primarily a demonstration of my point that Python programs don't need a `main` entry point like Java and C code does, while being an indicator of what is possible in relatively few lines of code. I quite deliberately wrote something that couldn't be turned in as the OP's own work, and hoped that they may ask questions about it in the comments. — Borodin, Oct 26 '14 at 10:50

score 0 · Answer 2 · edited May 23 '17 at 12:05

I do like Borodins answer but I don't think it left anything out of your original code (be sure to check it out and study it carefully).

Let's make 4 points here:

you don't need to create main() function in python
don't call function recursively this way, use loop
you put return number on invalid place, without it it should work correctly
you don't need to check id by hand, you can user dictionary for this

So dictionary:

# You can easily replace this code:
if answer == 1:
    position = "rock"
    print("You choose", position)
elif answer == 2:
    position = "paper"
    print("You choose", position)
elif answer == 3:
    position = "scissors"
    print("You choose", position)

# By this
import random
positions = {
    1: 'rock',
    2: 'paper',
    3: 'scissors'
}

# Later in the code
if answer in positions:
    position = positions[answer]
    print('You choose', position)
else:
    # Invalid value

Avoiding recursion and using loop:

position = None
while position is None:
    answer = int(input("Enter 1 for Rock, 2 for Paper, 3 for Scissors: "))

    if answer in positions:
        position = positions[answer]
        print('You choose', position)
    else:
        print('pick either 1, 2, or 3')

And now just apply it to your code:

import random
positions = {
    1: 'rock',
    2: 'paper',
    3: 'scissors'
}

for game_count in range(5):

    # Pick a value for player
    position = None
    while position is None:
        answer = int(input("Enter 1 for Rock, 2 for Paper, 3 for Scissors: "))

        if answer in positions:
            position = positions[answer]
            print('You choose', position)
        else:
            print('pick either 1, 2, or 3')


    # Computer picks what to play    
    number = random.randrange(1,4)
    print('Computer chooses', positions[number]) # Again, dictionary

    # NO return number here

    # if there is a tie
    if answer == number:
        print("It's a tie. Go again")
        continue

    # do more comparisons to decide who wins

I also assume you want to have 5 winning games (retry on tie), so just rewrite loop condition:

# Instead of
# for game_count in range(5):
games_to_go = 5
while games_to_go > 0:
    # ... 
    # if there is a tie
    if answer == number:
        print("It's a tie. Go again")
        continue

     # decrease number of games to go
     games_to_go -= 1

Rock, Paper, Scissors... can't seem to get it to work properly

2 Answers2