Python，覆盖父函数

Question

I've read a bunch of things here and on other sites about how to override functions, but none of them fit my needs.

I only need to change one line of code, so using super(Class, self).function(parameter) doesn't seem to help. I may be doing it completely wrong.

Anyway, here's the parent:

class Platformer(Entity):
    def __init__(self, color, width, height, x, y):
        Entity.__init__(self)
        pygame.sprite.Sprite.__init__(self)

        self.image = pygame.Surface([width, height])
        self.image.fill(color)

        self.rect = self.image.get_rect()
        self.rect.x = x
        self.rect.y = y

        self.xvel = 0
        self.yvel = 0
        self.onGround = False

    def update(self, up, down, left, right, platforms):
        if up:
            if self.onGround:
                self.yvel -= 8
                bounceSound.play()
        if down:
            self.yvel += 5
        if left:
            self.xvel = -3
        if right:
            self.xvel = 3
        if not self.onGround:
            self.yvel += 0.5
            if self.yvel > 15:
                self.yvel = 15
        if not(left or right):
            if self.onGround:
                self.xvel = 0

        self.rect.left += self.xvel
        self.collide(self.xvel, 0, platforms)
        self.rect.top += self.yvel
         self.onGround = False
        self.collide(0, self.yvel, platforms)

    def collide(self, xvel, yvel, plats):
        for p in platforms:
                if sprite.collide_rect(self, p) and isinstance(p, Block):
                    if xvel > 0:
                        self.rect.right = p.rect.left
                    if xvel < 0:
                        self.rect.left = p.rect.right
                    if yvel > 0:
                        self.rect.bottom = p.rect.top
                        self.onGround = True
                        self.yvel = 0
                    if yvel < 0:
                        self.rect.top = p.rect.bottom
                        self.yvel = 0

And this is the child that I wrote:

class Bird(Platformer):

    def update(self, up, down, left, right, platforms):
        if up:
            self.yvel -= 8
        if down:
            self.yvel += 5
        if left:
            self.xvel = -3
        if right:
            self.xvel = 3
        if not self.onGround:
            self.yvel += 0.5
            if self.yvel > 15:
                self.yvel = 15
        if not(left or right):
            if self.onGround:
                self.xvel = 0

Notice that all I want to change is the if statement in the "up" part of update . When running the program, everything works fine (bird gets drawn where it needs to be, its the right color, etc) except that update doesnt work.

Can someone help me to understand this? I really can't find the right syntax for this.

Answer 1

I would change the structure as follows:

In the parent add an extra parameter parentBehaviour :

def update(self, up, down, left, right, platforms, parentBehaviour=True):
    if up:
        if parentBehaviour and self.onGround:
            self.yvel -= 8
            bounceSound.play()
    #rest of method...

In the child:

def update(self, up, down, left, right, platforms):
    super(Bird, self).update(up, down, left, right, platforms, False)
    #end method

Reason for this structure, is generally you generally want to avoid duplicating your code. See Wikipedia for the DRY principle .