incorrect outputs in a python rock paper scissors game

Question

i have been trying to make a python rock paper scissors game with my limited python knowledge but good understanding of computer/ programming logic. here is my code:

def Main():
from random import randint

global computerChoice
global userChoice
print "Ok, let's play 3 rounds."

for i in range(3):
    userChoice = raw_input("Rock, paper, or scissors? ")

    computerChoice = randint(1,3)

    if userChoice == "Rock" or "rock":
        userChoice = 1
        choiceCompare()

    elif userChoice == "Paper" or "paper":
        userChoice = 2
        choiceCompare()

    else:
        userChoice = 3
        choiceCompare()

def choiceCompare():
global userChoice
global computerChoice

if userChoice == computerChoice:
    print "I chose the same thing! It's a draw!"

elif userChoice != computerChoice:

    if userChoice == 1:

        if computerChoice == 2:
            print "Yes! I chose paper, you lost!"

        elif computerChoice == 3:
            print "Dang. I chose scissors, you win."

    elif userChoice == 2:

        if computerChoice == 1:

            print "Man. I chose rock, you win."

        elif computerChoice == 3:

            print "I chose scissors, you loose!"

    else:
        if computerChoice == 1:
            print "Ha! I chose rock, you loose."

        elif computerChoice == 2:
            print "Aww, man! I chose paper, you win."


if __name__ == "__main__":
Main()

when i run it, i get completely wrong outputs like this:

Ok, let's play 3 rounds.
Rock, paper, or scissors? paper
I chose the same thing! It's a draw!
Rock, paper, or scissors? paper
I chose the same thing! It's a draw!
Rock, paper, or scissors? paper
Dang. I chose scissors, you win.

or this:

Ok, let's play 3 rounds.
Rock, paper, or scissors? scissors
Yes! I chose paper, you lost!
Rock, paper, or scissors? scissors
Yes! I chose paper, you lost!
Rock, paper, or scissors? scissors
Dang. I chose scissors, you win.

however, rock seems to be working fine:

Ok, let's play 3 rounds.
Rock, paper, or scissors? rock
Dang. I chose scissors, you win.
Rock, paper, or scissors? rock
I chose the same thing! It's a draw!
Rock, paper, or scissors? rock
Yes! I chose paper, you lost!

can anyone tell me what they think is wrong? thanks in advance, Liam.

P.S. i think there is something wrong with my choiceCompare function in the nested if statements. I'm not quite sure what though. also, ignore the automatic coloring in the bits where i copied the text from the program running, as they are not actually python code but text from the program.

you haven't got proper indentation in def choiceCompare, your also declaring the two global variables AGAIN which means they will not have the values you want — fr1tz, Apr 23 '14 at 00:41
I assume that the indentation issue is from pasting into Stack Overflow -- be careful with that in the future. Also, the global declaration does not impact the operation of the program -- though it is more than recommended against. — M. K. Hunter, Apr 23 '14 at 00:52
@fr1tz i'm pretty sure you have to declare the global variables in each function you use them in so that the function recognizes them. i had the problem of the second function saying that it couldn't find the global variable "userChoice" or the other, and so i put in the global thing and it fixed it. — theweasels1, Apr 23 '14 at 01:07

score 2 · Accepted Answer · edited May 23 '17 at 10:32

2

Your problem(s) start in these lines:

userChoice == "Rock" or "rock"

Either use userChoice.lower(), or use userChoice in ("Rock", "rock"). That'll help initially, and that's just at first glance.

To expand. The issue here is that you're comparing userChoice == "Rock", which is either True or False, then you're saying or "rock" which evaluates to True on its own (any non-empty string is True). See also: this answer on string truth values.

edited May 23 '17 at 10:32

Community

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answered Apr 23 '14 at 00:42

g.d.d.c

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That would be a nice syntax to have for readability's sake though. – Charles Clayton Apr 23 '14 at 00:58
thanks, i used the "userChoice in ("Rock", "rock")" and it solved the problem, but what is that doing vs the other thing you said, and just saying: "if userChoice == "rock" or userChoice == "Rock"' P.S. dont really know what "in" does, so that would also be good to know – theweasels1 Apr 23 '14 at 01:01
@theweasels1 - the `in` operator uses a class or object's `__contains__` method behind the scenes to test for membership inside of an iterable or other container. It's also the best way to determine if one string is a substring of another. The suggestion to use `.lower()` would allow you to accept any variation of rOck, RocK, ROCK, etc. It's coercing the entire user-supplied value to lower case before comparing. – g.d.d.c Apr 23 '14 at 01:15

score 0 · Answer 2 · answered Apr 23 '14 at 00:50

userChoice == "Rock" or "rock"

This line will always evaluate to true because it is like (userChoice == "Rock") or "rock" Try this instead: userChoice == "Rock" or userChoice == "rock"

See this link for documentation of boolean operators: https://docs.python.org/3.1/library/stdtypes.html

incorrect outputs in a python rock paper scissors game

2 Answers2