20 - classes.py

# Classes and Objects
"""Python is an object oriented programming language.
Almost everything in Python is an object, with its properties and methods.
A Class is like an object constructor, or a "blueprint" for creating objects."""

# Create a class
"""Create a class named MyClass, with a property named x"""


class MyClass:
    x = 5


# Create object
"""Create an object named p1, and print the value of x"""
p1 = MyClass()
print(p1.x)

# The __int__() function
"""To understand the meaning of classes we have to understand the built-in __init__() function.

All classes have a function called __init__(), which is always executed when the 
class is being initiated

Use the __init__() function to assign values to object properties, or other operations 
that are necessary to do when the object is being created"""

"""Create a class named Person, use the __init__() function to assign values for name and age:"""


class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age


p1 = Person("John", 36)

print(p1.name)
print(p1.age)
"""The __init__() function is called automatically every time the class is being 
used to create a new object"""

# Object methods
"""Objects can also contain methods. Methods in objects are functions that belong to the object"""


class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def myfunc(self):
        print("Hello my name is " + self.name)


p1 = Person("John", 36)
p1.myfunc()
"""The self parameter is a reference to the current instance of the class, and is used to access 
variables that belong to the class"""

# the self parameter
"""The self parameter is a reference to the current instance of the class, and is used to 
access variables that belongs to the class.

It does not have to be named self , you can call it whatever you like, but it has to be 
the first parameter of any function in the class"""


class Person:
    def __init__(mysillyobject, name, age):
        mysillyobject.name = name
        mysillyobject.age = age

    def myfunc(abc):
        print("Hello my name is " + abc.name)


p1 = Person("John", 36)
p1.myfunc()

# Modify object properties
p1.age = 40

# Delete object properties
del p1.age

# Delete objects
del p1

# The pass statement
"""class definitions cannot be empty, but if you for some reason have a class definition 
with no content, put in the pass statement to avoid getting an error."""