Why Does the Calculator Example Work Without a Constructor?

Excellent observation.

The answer is No, we're not missing the constructor. A class does not need to have a constructor.

This is completely valid Python:

class Calculator:

    def add(self, a, b):
        return a + b

    def multiply(self, a, b):
        return a * b

c = Calculator()

print(c.add(10, 5))
print(c.multiply(10, 5))

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Why Does It Work Without __init__()?

Because the Calculator object has no attributes that need initialization.

The methods:

def add(self, a, b):

and

def multiply(self, a, b):

simply take inputs and return results.

They don't need to store any data inside the object.

---

Think About It

When you create:

c = Calculator()

there is nothing to initialize.

The object doesn't need:

• name
• age
• brand
• balance

or any other stored data.

So a constructor is unnecessary.

---

Python Secret

Even though you didn't write a constructor, Python provides a default one.

Internally it's similar to:

class Calculator:

    def __init__(self):
        pass

    def add(self, a, b):
        return a + b

    def multiply(self, a, b):
        return a * b

Python automatically gives you an empty constructor.

---

When Do We Need a Constructor?

When an object must store data.

Example:

class Student:

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

Here:

s1 = Student("John", 20)

creates an object with data:

s1
├── name = John
└── age = 20

Without __init__(), those attributes wouldn't exist.

---

Calculator Example With Constructor

Suppose we want every calculator to remember its owner's name.

class Calculator:

    def __init__(self, owner):
        self.owner = owner

    def add(self, a, b):
        return a + b

c = Calculator("Rakesh")

print(c.owner)
print(c.add(10, 5))

Output:

Rakesh
15

Now we need a constructor because we're storing:

self.owner

inside the object.

---

Rule to Remember

Constructor Required

When the object needs to store data.

class Student:

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

---

Constructor Optional

When the class only provides behavior (methods).

class Calculator:

    def add(self, a, b):
        return a + b

---

Interview Question

Q: Is __init__() mandatory in Python classes?

Answer: No.

If you don't define a constructor, Python automatically provides a default empty constructor.

class Test:
    pass

obj = Test()  # perfectly valid

So the Calculator example is actually demonstrating an important idea:

A class can exist purely to provide methods, and such a class may not need any constructor or attributes at all.