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?
3 Answers
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
Comments
try:
if val is None: # The variable
print('It is None')
except NameError:
print ("This variable is not defined")
else:
print ("It is defined and has a value")
Comments
You can do this in a try and catch block:
try:
if val is None:
print("null")
except NameError:
# throw an exception or do something else
try : exceptblock to check if the error is being thrownNonesingleton)