为什么我收到unboundLocalError？

Question

Error I am getting is:

UnboundLocalError: local variable referenced before assignment?

Code:

def menu_option(index, count):
        import random
        random_number1 = random.randrange(1,31)
        random_number2 = random.randrange(1,31)
        if index == 1:
           problem = random_number1 + random_number2
        elif index == 2:
             problem = random_number1 - random_number2
        elif index == 3:
             problem = random_number1 * random_number2
        elif index == 4:
             problem = random_number1 // random_number2
        elif index == 5:
             problem = random_number1 % random_number2
        user_solution = get_user_solution(problem)
        return check_solution(user_solution, solution, count)

Answer 1

在最后一行return check_solution(user_solution, solution, count) solution变量未定义

Answer 2

Like Himanshu said It is because you have used a variable solution to which you haven't done any assignment. So in this case python looks for it inside function if not, it will look for it in global. if it doesn't find any assignment to it before being used it raises UnboundLocalError , also the variable problem is confined to if block so i think it is not accessible outside. So assign problem with some value before nested if block and also check solution variable about what should be assigned before passing it in function.

Answer 3

The chain of if/elif/elif ... suppose none of those conditions are met? Then problem is not assigned. But you try to use it in user_solution = get_user_solution(problem) . Looks like problem is the problem. The solution depends on what your design says should happen in this case. Is there a default that should be used? Raise your own exception? Return an error code? You have to decide that.