Python 错误：UnboundLocalError：赋值前引用了局部变量“score1”

Question

I am trying to make a simple dice roll game where two players roll a dice once for five rounds and the person with the highest score wins.

I have already tried setting the score1 variable to 0 within the function and outside of the function however this will cause the score to be reset to 0 every time.

#setting the scores as 0 before.
score1=0
score2=0

def round1():
    print('Round 1, lets go')
    input("Player 1 press ENTER to roll dice")
    diceroll1()
    input("Player 2 press ENTER to roll dice")
    diceroll2()
    round2()
#Round 1, calls upon dice roll functions and.

#dice roll function for player 1
def diceroll1():
    import random
    number = random.randint(1,6)
    print("Your number is: " + str(number))
    if number % 2 == 0:
        number = number + 10
        score1 = score1 + number
        print("Your new score is: " + str(score1))
    else:
        number = number - 5
        score1 = score1 + number
        print("Your new score is: " + str(score1))
    if score1 < 0:
        score1 = 0
    else:
        score1=score1

#dice roll function for player 2
def diceroll2():
    import random
    number = random.randint(1,6)
    print("Your number is: " + str(number))
    score2
    if number % 2 == 0:
        number = number + 10
        score2 = score2 + number
        print("Your new score is: " + str(score2))
    else:
        number = number - 5
        score2 = score2 + number
        print("Your new score is: " + str(score2))
    if score2 < 0:
        score2 = 0
    else:
        score2=score2

I want it to simply add the dice value to the score but I get this error :

UnboundLocalError: local variable 'score1' referenced before assignment

Answer 1

You should use the global identifier.

Some remarks about the code:

1. imports should be on the top of the code. And it is enough to import a library once.
2. You do not have to redefine the value of a variable to its own value. Like this score2 = score2 . Just don't do it.
3. I suggest you to use a while loop to make the game infinitely or a for loop for a const number of rounds.
4. Go through your code and count duplicates. There are a lot of them. Try to reduce the number.

I modified your code and left some interesting features there, that will help you in the future and now.

from random import randint


#setting the scores as 0 before.
score1=0
score2=0


#dice roll function for player 1
def diceroll1():
    global score1
    import random
    number = randint(1,6)
    print(f"Your number is: {str(number)}")

    number += - 5 if number % 2 else 10
    score1 += number

    if score1 < 0:
        score1 = 0

    print(f"Your new score is: {str(score1)}")


#dice roll function for player 2
def diceroll2():
    global score2
    import random
    number = randint(1,6)
    print(f"Your number is: {str(number)}")

    number += - 5 if number % 2 else 10
    score2 += number

    if score2 < 0:
        score2 = 0

    print(f"Your new score is: {str(score2)}")


def game_loop():
    for _ in range(int(input("Raound number: "))):
        print('Round 1, lets go')
        input("Player 1 press ENTER to roll dice")
        diceroll1()
        input("Player 2 press ENTER to roll dice")
        diceroll2()
        print()


if __name__ == "__main__":
    game_loop()

Next, try to make of those two functions one.

Answer 2

Use global . Using a global identifier is basically like calling it public , meaning it can be accessed from all the other parts of the code. global score1

Answer 3

This is Just a very common question for Python. Below is my answer in somewhere else.

global and nonlocal are very strange things when I was a beginner.

Just think about it: why do we need them in Python?

It is because we don't need var , let and such similar things to declare variables.

Think about Javascript , it is dynamic script language too and very alike to python, but it needs var or let or const to declare variables.

The most important thing of declaring variables is to determine scope.

So, in Python, our variables have implicit default scope: current scope where they are defined, and if we want to change scope of some variables, we need use global or nonlocal explicitly .

All names on the left side of = mean to define variables.

Before executing code of some certain scope, Python will pre-compute all local variables , which are those on the left side of = . This is why you got UnboundLocalError: local variable 'X' referenced before assignment in:

def foo():
    X = X + 10

So, if we look up those names not in defined current scope, just follow the rules of scope chain: up, up, up and until built_in .

Remember : scope of any name on the left side of = is default current scope, and you have to assign it(bind something to it) before referring it.

Global and local scope in python - Stack Overflow