How to test NoneType in python?

How to test NoneType in python?

So how can I question a variable that is a NoneType?

Use is operator, like this

if variable is None:

Why this works?

Since None is the sole singleton object of NoneType in Python, we can use is operator to check if a variable has None in it or not.

Quoting from is docs,

The operators is and is not test for object identity: x is y is true if and only if x and y are the same object. x is not y yields the inverse truth value.

Since there can be only one instance of None, is would be the preferred way to check None.

---

Hear it from the horses mouth

Quoting Pythons Coding Style Guidelines – PEP-008 (jointly defined by Guido himself),

Comparisons to singletons like None should always be done with is or is not, never the equality operators.

if variable is None:
   ...

---

if variable is not None:
   ...

How to test NoneType in python?

It can also be done with isinstance as per Alex Halls answer :

>>> NoneType = type(None)
>>> x = None
>>> type(x) == NoneType
True
>>> isinstance(x, NoneType)
True

isinstance is also intuitive but there is the complication that it requires the line

NoneType = type(None)

which isnt needed for types like int and float.