Difference between “if x” and “if x is not None”

Question

It appears that "if x" is almost like short-hand for the longer "if x is not None" syntax. Are they functionally identical or are there cases where for a given value of x the two would evaluate differently?

I would assume the behavior should also be identical across Python implementations - but if there are subtle differences it would be great to know.

Answer 1

Both "if x" and "if x is none" are not the same. If you run the statement "if x:"  checks whether x is assigned or not. If you execute the statement "if x is not none", is operator checks whether x is none or not. 

If you are still confused, Assign the values x = none, x = [], and x = 21 and run the following code. You can observe for x = none, no print statement will be executed, for x = [], only second print statement will be executed, and for x = 21, both the print statements will be executed.

if x: 

    print ('if x' )

if x is not None:

    print( 'if x is not None')

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