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 vote162 views1 answer
Pandas find list based on condition
Python
0 vote224 views1 answer
Del no of elements in lis
Python
-2 votes158 views2 answers
Django form date picker
Python
1 vote171 views2 answers
Beautifulsoup python set text
Python
1 vote120 views1 answer
Da
Python
0 vote178 views1 answer
Python Remove Character from String using translate()
Python
3 votes160 views1 answer
Python how to find the highest number in a dictionary
Python
1 vote189 views1 answer
Flask form errors
Python Flask
0 vote205 views1 answer
How to delete lists after using them in python
Python
2 votes169 views1 answer
How i install jupyter notebook in a new conda virtual environment
Python