What is the difference between "is None" and "== None"

user_327508 0
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I recently came across this syntax, I am unaware of the difference.

I would appreciate it if someone could tell me the difference.

python
5 Answers

It depends on what you are comparing to None. Some classes have custom comparison methods that treat == None differently from is None.

In particular the output of a == None does not even have to be boolean !! - a frequent cause of bugs.

For a specific example take a numpy array where the == comparison is implemented elementwise:

import numpy as np
a = np.zeros(3) # now a is array([0., 0., 0.])
a == None #compares elementwise, outputs array([False, False, False]), i.e. not boolean!!!
a is None #compares object to object, outputs False
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