🔍 Python Operators: is vs in

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.

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✅ What is the is Operator?

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")

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✅ What is the in Operator?

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

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🔁 Side-by-Side Comparison

Expression	Description	Output
a is b	True if a and b are same object	True
a == b	True if a and b have same value	True
x in y	True if x is inside container y	True/False

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⚠️ Common Mistakes

• ❌ 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.

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🧠 Final Thoughts

• 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!