Pythagotchi - Part 4


We want to be able to make the egg wobble, but we also want to be able to define different animations later on too. To do this, we’re going to define each new animation as a new function in our Creature class, and then use the update() function to call it.

Let’s start off creating the animation function. We’ll call it wobble():

class Creature(object):
    def __init__(self, window, canvas, x=0, y=0):
    def update(self):
    def wobble(self):
        self.x += 1
        if self.x > 103:
            self.x -= 5
            self.animation_timer = 100
    def draw(self):

The animation is very basic, it simply moves the egg to the right a little, then pulls it back again. We’ve also created a new attribute for our Creature class - animation_timer. We need to initialise this in the __init__() function, so add the following line:

        self.animation_timer = 0

put it just above the call to self.window.after(5, self.update).

Next we want to update our update() function. Delete what’s there currently and replace it with this:

    def update(self):
        if self.animation_timer == 0:
            self.animation_timer -= 1
        self.window.after(5, self.update)

Every time our new update() function is called, it checks to see if the animation timer has expired (equal to zero), if it isn’t, it simply decreases it by one. If it is, it calls a mysterious current_animation() function. We’ll define that right now. Up in your __init__() function, add the following line just above the self.animation_timer = 0 line that you added a minute ago:

        self.current_animation = self.wobble

Python is very flexible with its variables. Here we’re making a variable point to a whole other function! This means simply changing where current_animation points will cause our update() function to execute that animation instead, without us having to change any code! Very handy.

At this stage, you should be able to run your program and you should see your egg sit wobbling ever-so-slightly every once in a while. The frequency of this animation is controlled in the wobble() function, where it sets a new value for the animation_timer variable. Try making the animation happen more often.

See if you can define a second animation, maybe a ‘hop’ animation. Can you make it wobble a few times then hop, then go back to wobbling? You might need to create a new ‘timer’ to make that work.

Once you’ve played around with the very basic animations we can achieve this way, move on and we’ll have a go at making some more interesting ones using different image frames.

Before we can do that though, we need to do a bit more drawing.