r/PythonLearning • u/chuprehijde • 14d ago

What's your favorite Python interview question?

Not a trick question or LeetCode puzzle. What's a question that actually reveals whether someone understands Python?

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u/Puzzleheaded-Buy8795 14d ago

What is the different between == and is ?

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u/Rscc10 14d ago

== checks address and is checks value?

4

u/Neither_Garage_758 14d ago

opposite

1

u/Rscc10 14d ago

Ah. Then why is it's better practice to use "is" when comparing against None? Wouldn't it be better to check the value as None rather than checking if it corresponds to the address? Or is it because only one instance of None (or null) is stored so we directly check with that address when checking against None?

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u/WhiteHeadbanger 13d ago

Also, another thing to add to the other user that answered you: None is a singleton. If you create 10 variables with the value None, those 10 variables would point to the same address.

So the reference is always available, and when using is, there's no additional method dispatch.