What is the difference between "is None" and "== None"
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.
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"
class Foo:
def __eq__(self,other):
return True
foo=Foo()
print(foo==None)
# True
print(foo is None)
# False