Master Python OOP: Class Attributes, Methods, Inheritance, super() & @property

1. Basic Use of Object‑Oriented Classes

Key Points

Attributes: class attributes and instance attributes

Methods: instance methods, class methods, static methods

A class can access its class attributes, class methods, and static methods

Code Example

class A(object):
    # class attribute
    class_a = 20

    def __init__(self):
        # instance attribute
        self.a = 10

    # instance method
    def a_print(self):
        print("a_print")

    # class method
    @classmethod
    def class_print(cls):
        print('class_print')

    # static method
    @staticmethod
    def static_print():
        print("static_print")

# Access class attribute (cannot access instance attribute directly)
print(A.class_a)
# Access instance attribute via an object
print(A().a)
# Call class method
A.class_print()
# Call static method
A.static_print()
# Two ways to call instance method
A.a_print(A())
A().a_print()

2. Class Calls and Attribute Access

Key Points

To invoke another class's methods or attributes within a class, use inheritance or attribute assignment.

Code Example

# Inheritance
class B(A):
    def b_print(self):
        print("b_print")

B().b_print()
B().a_print()

# Attribute‑assignment style
class C(object):
    obj_a = A()
    def c_print(self):
        print('c_print')

# Call method of A through C's attribute
C.obj_a.a_print()

3. Using super() and @property

Key Points

super() calls a method from the parent class.

Typical scenario: override a parent method and extend its behavior.

@property allows a method to be accessed like an attribute, without parentheses.

Code Example

class A(object):
    def a_print(self):
        print("a_print")

class B(A):
    def a_print(self):
        # call parent method
        super().a_print()
        print("add_data")

    @property
    def data(self):
        print("data")

B().a_print()
# Access method as property
B().data