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

1 vote170 views1 answer
Python background function
Python
0 vote187 views1 answer
Distance matrix gogle map python
Python
1 vote177 views1 answer
How to clear a pickle file
Python
0 vote289 views2 answers
Django admin image
Python Django
2 votes192 views2 answers
Tkinter button foreground color click
Python
2 votes182 views1 answer
Python read text file into a list
Python
0 vote197 views1 answer
Python find equal rows of two numpy arrays
Python
2 votes175 views2 answers
Change the color of the button on hovering tkinter
Python
-2 votes196 views1 answer
Calculate sum in 2d list python
Python
1 vote187 views2 answers
Use Python to calculate (((1+2)*3)/4)^5
Python