Lesson 7

Download and extract the image files below.

media.zip

State

We can add behavior to our sprite’s by defining different states. For example, a sprite can perform one type of behavior if it is in one state, and perform another behavior if it is in a different state. Add a custom property to the sprite to store its current state. If only two behaviors are required, a boolean will suffice. For example,

self.is_in_original_state = True

Then, in on_update use a conditional to define the different behaviors. For example,

def on_update(self, dt):
    if self.is_in_original_state:
        self.x += 1
    else:
        self.x -= 1

Mouse Click Event Handler

In Pycat, when a sprite is clicked with the left mouse button, the on_left_click() event handler is called.

def on_left_click(self):
    pass

Tagging Sprites

self.add_tag('alien')

if self.is_touching_any_sprite_with_tag('alien'):
    print("I touched an alien!")

Labels

Labels display strings on the screen. The Label API is very similar to the Sprite’s API. For example,

label = w.create_label()
label.x = 100
label.y = 300
label.text = 'Hello, World!'

will create a new label, set the x and y position, and display ‘Hello, World!’ in the window.

You can also create a custom Label class very similar to the way you would a custom Sprite class.

class Hello(Label):
    def on_create(self):
        self.text = 'Hello'

    def on_update(self, dt):
        pass

window.create_label(Hello)

Sound Effects

You can use the pycat Player class to play different sounds. First you must find a .wav sound file you would like to play in your game. Scratch has many good sound effects that you can download.

sound = Player('die.wav')
sound.play()