将参数更改为 python 中的 boolean 值

Question

I was trying to create a back button in pygame using python but my parameter(condition) is not being set to false, how do I do this? Here is my code:

def back(condition):  #condition - any boolean variable in my script
    mouse = pygame.mouse.get_pos()
    click = pygame.mouse.get_pressed()

    if 5 + 125 > mouse[0] > 5 and 5 + 125 > mouse[1] > 5:
        gameDisplay.blit(backBtn, (5, 5))
        if click[0] == 1:
            if condition:
                condition = False
    else:
        gameDisplay.blit(backBtn_hover, (5, 5))
    

If you have any sort of answer please answer.

Thank you: :D

Answer 1

Since condition is of an immutable type, any change to it is only visible inside the function.

You will need to return it and assign it back when calling the function.

def back(condition):  #condition - any boolean variable in my script
    mouse = pygame.mouse.get_pos()
    click = pygame.mouse.get_pressed()

    if 5 + 125 > mouse[0] > 5 and 5 + 125 > mouse[1] > 5:
        gameDisplay.blit(backBtn, (5, 5))
        if click[0] == 1:
            if condition:
                condition = False
    else:
        gameDisplay.blit(backBtn_hover, (5, 5))
    return condition

...

condition = back(condition)

It is usually not advisable to make it a global variable so I'm not going to suggest that.

Answer 2

Do you expect this to happen?

condition = True
back(condition)
print(condition) # False

That's not how Python works. You can't change variables passed to functions. Something like that would work.

container = { 'condition': True }
back(container)
print(container['condition']) # False

Because in this case you don't change the variable, but its content. But anyway it's bad code. Normally you would do something like that:

condition = True
condition = back(condition)
print(condition) # False

Of course you need to add a return statement to your function.

Answer 3

Your answer likely is due to scoping of your variables, three examples provided below that hopefully will lead you to a solution:

Situation 1

condition = True

def back(condition):
    condition = False
    print(f"{condition=}")


def main():
    local_condition = back(condition)
    global_condition = condition
    print(f"{local_condition=}\n{global_condition=}")


if __name__ == '__main__':
    main()

Results:

condition=False
local_condition=None
global_condition=True

Situation 2 with added return in back funciton

condition = True

def back(condition):
    condition = False
    print(f"{condition=}")
    return condition

def main():
    local_condition = back(condition)
    global_condition = condition
    print(f"{local_condition=}\n{global_condition=}")


if __name__ == '__main__':
    main()

Results 2:

condition=False
local_condition=False
global_condition=True

Situation 3 redefining global

condition = True

def back(condition):
    condition = False
    print(f"{condition=}")
    return condition

def main():
    global condition
    condition = back(condition)
    global_condition = condition
    print(f"{condition=}\n{global_condition=}")


if __name__ == '__main__':
    main()

Results 3:

condition=False
condition=False
global_condition=False