Lesson 1
Download and extract the image files below.
Import Statements
Import statements allow us to import code from outside the file we are currently working on. For example, Window and Sprite are pieces of code that we have already written and would like to re-use.
from pycat.core import Window, Sprite
Variables
Variables let us store and manipulate data. They store simple data like a number or a string of characters or more complex objects like a Window or a Sprite.
message = 'enter your name'
number = 100
window = Window()
elephant = window.create_sprite()
Properties
Properties, also known as member variables, are variables contained inside a particular Class like Sprite or Window. For example, below image, x, y, and scale are properties of the Sprite class.
elephant.image = 'elephant.png'
elephant.x = 500
elephant.y = 400
elephant.scale = 1.5
Functions
Functions define a sub-routine in our program. They are handy to eliminate duplicate code and make our programs easier to understand and maintain. The data we pass into functions are called arguments. The data that we receive from functions are called return values. The code inside functions is not executed until the function is called.
Two functions in the Python programming language are input() and print().
age = input('enter your age:')
print('your age is', age)
Methods
Methods, also known as member functions, are functions contained inside a particular class. Thus, we usually need an instance of the class to call them.
The method create_sprite() is a member of the Window class and goto_random_position() is a method in the the Sprite class.
elephant = window.create_sprite()
elephant.goto_random_position()
Conditional Statements
Conditional statements change the flow of our code based on some logic.
size = input('big or small? )
if size == 'big':
elephant.scale = 2
elif size == 'small':
elephant.scale = 0.5
else:
print('Sorry, I only understand big or small.')