12. Difference between == and "is" operators in Python

12. Is None or == None, what should you use, and why? Is there a difference between == and is operators?

Yes, there is a difference between is and ==, and when dealing with None, it's important to choose the right one.

✅ Short Answer:

Always use is None or is not None, not == None.

a = [1, 2, 3]
b = [1, 2, 3]
print(a is b)  # False (different objects)
print(a == b)  # True (equal values)

🧠 Detailed Explanation:

🔹 is checks identity

• It checks whether two variables refer to the same object in memory.
• None is a singleton in Python — there's only one instance of it.

x = None
if x is None:
    print("x is None")  # ✅ preferred

🔹 == checks equality

• It checks whether two values are equal (using the __eq__() method).
• It can be overridden in custom classes.

class Weird:
    def __eq__(self, other):
        return True

w = Weird()
print(w == None)  # True (misleading!)
print(w is None)  # False (correct!)

This is why == None can lead to unexpected behavior, especially when working with objects that redefine equality.

✅ Best Practice:

🧪 Quick Comparison:

🔐 TL;DR:

✅ Use is None and is not None — it's the Pythonic and reliable way to test for None.