Python Class/Objects

Python 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.

How to create a class:

To create a class, use the keyword class

Example:

class FirstClass:
  x = 5

print(FirstClass)

Output:

<class '__main__.FirstClass'>

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Create Object:

Example:

class FirstClass:
  x = 10

p = firstClass()
print(p.x)

Output:

10

Note: Here p is an object of class (FirstClass).

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__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:

Example:

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

p = Person("Billy", 36)

print(p.name)
print(p.age)

Output:
Billy
36

Note: __init__() function is called automatically every time the class is being used to create a new object.

Note: self represents the instance of the class. By using the “self” keyword we can access the attributes and methods of the class in python

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Object Methods

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

Example:

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

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

p = Person("Billy")
p.myfunc()

Output:

Hello my name is Billy

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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.

We can call self with any name, but it has to be the first parameter of any function in the class.

Example:

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

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

p1 = Person("Billy")
p1.myfunc()

Output:

Hello my name is Billy

Note: We have named self as my and abc.

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Modifying object properties:

Example:

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("Billy", 36)
p1.age = 40
print(p1.age)

Output:

40

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Delete Object Properties:

You can delete properties on objects by using the del keyword.

Example:

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("Billy", 36)

del p1.age

print(p1.age)

Output:

Traceback (most recent call last):
  File "demo_class7.py", line 13, in <module>
    print(p1.age)
AttributeError: 'Person' object has no attribute 'age'

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