What is the difference between is None and None

Question

I recently came across this syntax  I am unaware of the difference    I would appreciate it if someone could tell me the difference

User · Answer

In this case  they are the same  None is a singleton object  there only ever exists one None    is checks to see if the object is the same object  while    just checks if they are equivalent   For example   p    1  q    1  p is q   False because they are not the same actual object p    q   True because they are equivalent   But since there is only one None  they will always be the same  and is will return True   p   None q   None p is q   True because they are both pointing to the same  None

User · Answer

The answer is explained here   To quote      A class is free to implement   comparison any way it chooses  and it   can choose to make comparison against   None mean something  which actually   makes sense  if someone told you to   implement the None object from   scratch  how else would you get it to   compare True against itself      Practically-speaking  there is not much difference since custom comparison operators are rare   But you should use is None as a general rule

User · Answer

If you use numpy   if np zeros 3   None  pass   will give you error when numpy does elementwise comparison

User · Answer

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

User · Answer

class Foo      def   eq   self other           return True foo Foo    print foo  None    True  print foo is None    False

[python] What is the difference between "is None" and "== None"

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