Undef variable

Testing if a Variable Is Defined
Credit: Hamish Lawson

Problem
You want to take different courses of action based on whether a variable is defined.

Solution
In Python, all variables are expected to be defined before use. The None object is a value you often assign to signify that you have no real value for a variable, as in:

try: x
except NameError: x = None
Then it’s easy to test whether a variable is bound to None:

if x is None:
    some_fallback_operation(  )
else:
    some_operation(x)

Source: oreilly.com

Similar codes

0 vote126 views1 answer
Travis deployment script for django applications to heroku
Python
0 vote115 views1 answer
Credential not provided when i try to sign up a new user django
Python
19 votes117 views6 answers
Remove columns from a dataframe python
Python
2 votes111 views1 answer
Python string remove whitespace and newlines
Python
0 vote108 views1 answer
Print start time in python
Python
-1 vote121 views2 answers
Make a pop up window in python
Python
0 vote114 views1 answer
Any(iterable)
Python
0 vote150 views1 answer
Static files not loading 404 error django
Python Django
3 votes109 views6 answers
Python variable
Python
1 vote116 views1 answer
Button position python
Python