Python: how is `None` evaluated in logical expressions, in relation to other boolean values?

Question

In Python 3...

• Sample 1:

s: str = None
b: bool = True
b = (s != None) and (s != "some-not-allowed-value")
print (b)

Displays False (as it seems intuitive)

---

• Sample 2:

s: str = None
b: bool = True
b = (s) and (s != "some-not-allowed-value")
print (b)

Displays None

Why ? How is that s field evaluated ?

Answer 1

In python, None interacts as follows with booleans:

>>> print(None and False)
None
>>> print(None and True)
None
>>> print(None or False)
False
>>> print(None or True)
True

Note that the type hints (s: str) are only hints, and are ignored at Runtime