At the heart of OOP are classes and objects. A class defines a blueprint or prototype from which individual objects are created. The class encapsulates data for the object and methods to manipulate that data.
In Python, a class is defined using the class keyword. The naming convention is to use CamelCase notation for class names.
Example:
class Student:
pass
This is the simplest form of a class, which does nothing and is just a placeholder.
The __init__ method is a special method called a constructor, automatically called when you create an object from a class. It is used to initialize the attributes of an object.
Example:
class Student:
def __init__(self, name, age):
self.name = name
self.age = age
Here, name and age are attributes of the Student class. The self parameter refers to the object itself.
An object is an instance of a class. To create an object, you call the class as if it were a function.
Example:
# Creating an object of Student class
student1 = Student("Alice", 20)
print(student1.name) # Outputs: Alice
print(student1.age) # Outputs: 20
A method is a function defined inside a class and is used to define behaviors of an object.
Example:
class Student:
def __init__(self, name, age):
self.name = name
self.age = age
def introduce(self):
return f"My name is {self.name} and I am {self.age} years old."
student1 = Student("Bob", 22)
print(student1.introduce()) # Outputs: My name is Bob and I am 22 years old.
Object attributes can be modified directly or via methods defined in the class.
Example:
class Student:
# ... [previous code]
def set_age(self, age):
self.age = age
student1 = Student("Charlie", 18)
print(student1.age) # Outputs: 18
student1.set_age(19)
print(student1.age) # Outputs: 19
You can delete objects and their attributes using the del keyword.
Example:
student2 = Student("David", 21)
print(student2.age) # Outputs: 21
# Delete the age attribute
del student2.age
# Delete the student2 object
del student2
__str__ MethodThis method allows us to define a user-friendly or informative representation for our object, which gets called with the print() function or str().
Example:
class Student:
# ... [previous code]
def __str__(self):
return f"Student(name={self.name}, age={self.age})"
student3 = Student("Eva", 23)
print(student3) # Outputs: Student(name=Eva, age=23)
Classes provide a means of bundling data and methods operating on that data within one unit. By understanding how to create classes and objects, you set the foundation for more advanced OOP principles like inheritance, polymorphism, and encapsulation. The ability to define and manipulate your own data types via classes is a powerful tool in a programmer’s toolkit.