How to test a variable is null in python [duplicate]

Question

val = ""  del val  if val is None:     print("null") 

I ran above code, but got NameError: name 'val' is not defined.

How to decide whether a variable is null, and avoid NameError?

Answer 1

Testing for name pointing to None and name existing are two semantically different operations.

To check if val is None:

if val is None:     pass  # val exists and is None 

To check if name exists:

try:     val except NameError:     pass  # val does not exist at all