The init Constructor

So far, you created objects first, then added attributes later.

tom = Student()
tom.name = "Tom"
tom.score = 85

There is a better way.

Python gives us __init__() to set up objects when they are created.

What Is init()?

__init__() is a special method called automatically when you create an object.

It is used to give starting values to attributes.

Why It Matters

It helps you:

• create objects faster
• avoid missing attributes
• keep code cleaner
• give every object a clear starting state

Basic Structure

class ClassName:
    def __init__(self, value):
        self.attribute = value

First Example

class Student:
    def __init__(self, name):
        self.name = name

tom = Student("Tom")
print(tom.name)

Output

Tom

Two Attributes

class Student:
    def __init__(self, name, score):
        self.name = name
        self.score = score

sara = Student("Sara", 92)

print(sara.name)
print(sara.score)

Output

Sara
92

How It Works

When you run:

sara = Student("Sara", 92)

Python automatically runs:

__init__(self, "Sara", 92)

and saves the values.

Add Other Methods Too

class Student:
    def __init__(self, name, score):
        self.name = name
        self.score = score

    def show_info(self):
        print(self.name, self.score)

tom = Student("Tom", 85)
tom.show_info()

Output

Tom 85

Multiple Objects

tom = Student("Tom", 85)
sara = Student("Sara", 92)

print(tom.name)
print(sara.name)

Output

Tom
Sara

Common Beginner Errors

Forgetting self

def __init__(name):

Wrong.

Use:

def __init__(self, name):

Wrong Number of Values

If __init__() expects two values, give two values.

Code Along

Create a class called Book.

Use __init__() with:

• title
• price

Create one book and print both values.

Mini Challenge

Create a class called Phone.

Steps:

• Use __init__() with:

  • brand
  • model
  • price

• Create:

phone1 = Phone("Apple", "iPhone", 999)

• Print all values

Expected output:

Apple
iPhone
999

Real World Use Case

Apps use constructors to create users, products, orders, bank accounts, and game characters with starting data.

Quiz

1. What is __init__()?
2. When does it run?
3. Why is it useful?
4. Can a class have other methods too?

Assignment

Create a class called Car with brand and color using __init__().

Summary

You learned how __init__() gives objects starting values when they are created.