Understanding __init__ in Python: How It Differs from Regular Functions Like print()

When learning Python and exploring object-oriented programming (OOP), beginners often encounter something that looks like a function but behaves differently:

def __init__(self, ...):

At first glance, it seems like we’re just defining a function inside a class. But what’s really going on? Why doesn’t this behave like a regular function like print() or len()? Let’s break it down.

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🔸 Is __init__ a Function?

Yes — __init__ is a function, but it’s a special kind of function in Python known as a dunder method (short for “double underscore”).

More specifically, __init__ is a constructor. It’s automatically called when a new object is created from a class. You can think of it as a setup function that runs only once when you create an object.

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🔹 Example: Defining a Class With __init__

class Person:
    def __init__(self, name, age):
        print("Initializing a new Person object...")
        self.name = name
        self.age = age

Now when you create a new Person object:

p1 = Person("Alice", 30)

This automatically triggers:

__init__(self=p1, name="Alice", age=30)

Which sets:

p1.name = "Alice"
p1.age = 30

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🔸 How __init__ Differs From Regular Functions

Let’s compare it to a built-in function like print():

Feature	print()	__init__()
Where it lives	Globally available	Inside a class
When it’s called	When you type print(...)	Automatically, when you create an object
Purpose	Display information	Initialize object data
Defined by	Python’s standard library	You (in your class definition)

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🔹 Each Class Has Its Own __init__

Unlike built-in functions which are defined once and reused globally, each class in Python defines its own version of __init__, tailored to what that class represents.

✨ Example: Two Different __init__ Methods

class Dog:
    def __init__(self, breed):
        self.breed = breed

class Car:
    def __init__(self, brand, year):
        self.brand = brand
        self.year = year

Usage:

d = Dog("Labrador")
c = Car("Toyota", 2020)

print(d.breed)   # Labrador
print(c.brand)   # Toyota
print(c.year)    # 2020

The Dog class and Car class both have their own custom initialization logic, defined by their own __init__ methods.

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🔁 Summary

Concept	Meaning
__init__	Special method to initialize a new object
Defined per class	Yes, each class has its own __init__
Called automatically	Yes, when you create an object like obj = Class()
Purpose	Set up the initial state of the object
Difference from print()	print() is global and reused; __init__ is class-specific

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🧠 Final Thoughts

The __init__ method may look like just another function, but it plays a key role in Python’s object-oriented design. Think of it as the birth script for every object — customizing how it starts its life. And unlike regular functions like print() or input(), __init__ is yours to define inside each class, making it incredibly flexible and powerful.

Want to practice? Try creating your own class with __init__ and explore how object data is stored and accessed. It’s one of the most fundamental skills in Python programming!

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