Python practice game, issue with switching between while loops

Question

I want these while loops on line 21 - 34 to alternate (one ends the next one begins) but one simply stops and the next one doesn't run.

def update(self):
    mv_p = False
    while not mv_p:
        self.rect.x -= 5
        if self.rect.left > width - 750:
            mv_p = True
            return mv_p
            break

    while mv_p:
        self.rect.y += 5
        if self.rect.right < width - 750:
            mv_p = False
            return mv_p
            break

Answer 1

Calling return inside of a loop will break function/method execution and return value to the caller.

So, as soon as the first loop returns mv_p , your method call is over.

Answer 2

If you want them to alternate (first loop, second loop, first loop, second loop, etc), you should nest them inside another loop.

def update(self):
    mv_p = False
    while True:
        while not mv_p:
            self.rect.x -= 5
            if self.rect.left > width - 750:
                mv_p = True
                break

        while mv_p:
            self.rect.y += 5
            if self.rect.right < width - 750:
                mv_p = False
                break

        #need to draw on the screen here or nothing will be shown
        #add condition to exit the function, adding for example a return
        #inside af if, otherwise this will be an infinite loop.

If instead you just want first loop, second loop and exit no need to nest them, just remove the return calls from your function.