Understanding the difference between is and in in Python is really important — especially when you're trying to write clean and bug-free code. In this short guide, I’ve shared my learning and examples that helped me understand how these two operators work differently.

The is operator checks identity, not equality.

• It returns True if two variables refer to the same object in memory.
• It’s often used to check if something is None.

a = [1, 2, 3] b = a c = [1, 2, 3] print(a is b) # True – same memory reference print(a is c) # False – different objects even if content is same

🔸 Use is when you care about object identity, not just if values match.

A good use case:

x = None if x is None: print("x has no value")

The in operator checks membership — it tells you if a value exists inside a list, string, tuple, dictionary, etc.

fruits = ["apple", "banana", "cherry"] print("banana" in fruits) # True print("grape" in fruits) # False

It also works with strings:

text = "hello world" print("world" in text) # True print("python" in text) # False

• ❌ Using is to compare values:

  a = 1000 b = 1000 print(a is b) # Might be False even though a == b

• ✅ Use == when comparing values, and use is for identity:

  print(a == b) # True

• ✅ Always use is None, not == None.

• Use is when comparing with None or checking identity.
• Use in to check if a value exists inside something.
• Don't mix them up — Python won’t stop you, but your bugs will get harder to find!