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 vote211 views1 answer
Django update replace regex
Python Django
0 vote158 views1 answer
How to access http page in pythion
Python
0 vote151 views1 answer
Origin in CORS_ORIGIN_WHITELIST is missing scheme or netloc
Python
5 votes143 views3 answers
How to calculate mean in python
Python
2 votes157 views1 answer
Python Crash Course, 2nd Edition: A Hands-On, Project-Based Introduction to Programming
Python
0 vote157 views1 answer
Soup.find_all attr
Python
62 votes167 views6 answers
Python loop with index
Python
65 votes152 views4 answers
Python randomize list
Python
0 vote159 views1 answer
Pandas unqiue value each column
Python
0 vote188 views1 answer
Create and add many to many field in django
Python Django