Why does this lambda function always return False even when the type matches?

Question

Given:

type(m[11].value)
<class 'NoneType'>

type(m[12].value)
<class 'str'>

Why then does the following lambda function always return false when I pass it the two above vars?

g = lambda x: type(x) is None

Answer 1

You're checking whether the type of an object is None, and not the actual object itself. type returns a type object, the actual type/class of that object. In the particular case of None, it returns NoneType:

>>> type(None)
NoneType

Since object has a type, type(x) is None will never evaluate to True.

Why not just test the object directly? Additionally, if you are going to name a lambda, you may as well define your own function.

>>> def check(x):
...     return x is None
... 
>>> check(None)
True  

Alternatively, you may use an isinstance check -

>>> isinstance(None, type(None))
True

As a side note, the pd.isnull function from the pandas library provides this functionality directly.