如何在Python 3中的多个不同函数中使用变量

Question

I define a variable named 'computerChoice' in a function and then attempt to use it in another variable but it says that 'computerChoice' is undefined... Being new to Python, I am not sure why this is happening so I hope that you could help answer my question!

def computerDecision():
            import random
            for x in range(1):
            num = random.randint(1,4)
            if num == 1:
                computerChoice = 'rock'
            elif num == 2:
                computerChoice = 'paper'
            elif num == 3:
                computerChoice = 'scissors'

    def determineWinner():
        if userInput == computerChoice:
            print("You both chose " + computerChoice)
            print("DRAW!")
        elif userInput == 'rock' and computerChoice == 'paper':
            print("The computer chose " + computerChoice)
            print("COMPUTER WINS!")
        elif userInput == 'rock' and computerChoice == 'scissors':
            print("The computer chose " + computerChoice)
            print('USER WINS!')
        elif userInput == 'paper' and computerChoice == 'rock':
            print("The computer chose " + computerChoice)
            print("USER WINS!")
        elif userInput == 'paper' and computerChoice == 'scissors':
            print("The computer chose " + computerChoice)
            print("COMPUTER WINS!")
        elif userInput == 'scissors' and computerChoice == 'rock':
            print("The computer chose " + computerChoice)
            print("COMPUTER WINS!")
        elif userInput == 'scissors' and computerChoice == 'paper':
            print("The computer chose " + computerChoice)
            print("USER WINS!")

Answer 1

The computerChoice variable is restricted in scope to the function in which it was defined. This is to prevent functions from interfering with one another. You can declare it to be global (accessible from anywhere) with the keyword global :

global computerChoice

This is probably not what you want, however, as your functions do not need to interact with each other. You can just make computerDecision() return its choice.

import random
def computerDecision():
    for x in range(1):
        num = random.randint(1,4)
        if num == 1:
            return 'rock'
        elif num == 2:
            return 'paper'
        elif num == 3:
            return 'scissors'

def determineWinner():
    computerChoice = computerDecision()
    if userInput == computerChoice:
        print("You both chose " + computerChoice)
        print("DRAW!")
    elif userInput == 'rock' and computerChoice == 'paper':
        print("The computer chose " + computerChoice)
        print("COMPUTER WINS!")
    elif userInput == 'rock' and computerChoice == 'scissors':
        print("The computer chose " + computerChoice)
        print('USER WINS!')
    elif userInput == 'paper' and computerChoice == 'rock':
        print("The computer chose " + computerChoice)
        print("USER WINS!")
    elif userInput == 'paper' and computerChoice == 'scissors':
        print("The computer chose " + computerChoice)
        print("COMPUTER WINS!")
    elif userInput == 'scissors' and computerChoice == 'rock':
        print("The computer chose " + computerChoice)
        print("COMPUTER WINS!")
    elif userInput == 'scissors' and computerChoice == 'paper':
        print("The computer chose " + computerChoice)
        print("USER WINS!")

Also note that computerDecision() can be redefined more simply, as just return random.choice(("rock", "paper", "scissors")) .