Why does 'if not None' return True?

Question

I'm having trouble understanding this

I tried:

if not None:
    print('True')

Why does it print True? Isn't the None type supposed to be None?

Answer 1

In Python None is a singleton. It is called the null in other languages.

In your if not None:, the compiler assumes that not None means non empty, or non-zero and we know an if statement evaluates non-zero values as True and executes them.

Function Examples:

1) if not None: prints argument x in test()

   def test(x):
       if not None:
           print(x)

   >>> test(2)
   2

2) if 1: prints argument x in test()

   def test(x):
       if 1:
           print(x)

   >>> test(2)
   2

3) if -1: prints argument x in test()

   def test(x):
       if -1:
           print(x)

   >>> test(2)
   2

4) if 0: does not prints argument x in test()

   def test(x):
       if 0:
           print(x)

   >>> test(2)

5) if True: prints argument x in test()

   def test(x):
       if True:
           print(x)

   >>> test(2)
   2