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 vote245 views1 answer
How to insert files in tuple python
Python
0 vote282 views1 answer
2 functions at a time py
Python
0 vote255 views1 answer
Python priority queue stack overflow
Python
1 vote257 views2 answers
Left click pyautogui
Python
1 vote270 views1 answer
Convert all values in array into float
Python
1 vote241 views2 answers
Pedagogical example
Python
21 votes245 views5 answers
Basic tkinter window
Python
0 vote311 views1 answer
Find the closest smaller value in an array python
Python
0 vote260 views2 answers
Selenium screenshot python user agent
Python
1 vote201 views1 answer
Python os module open a text file
Python