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 vote233 views1 answer
Is python idle an ide
Python
1 vote238 views1 answer
Gimp python
Python
4 votes224 views3 answers
Unable to locate package python-pip
Python
0 vote230 views3 answers
Print out session information django
Python
6 votes217 views1 answer
Pandas select row with substring
Python
0 vote232 views1 answer
Label with list comprehension python
Python
0 vote211 views1 answer
How to colour a specific cell in pandas dataframe
Python
5 votes210 views2 answers
Random boolean python
Python
0 vote304 views1 answer
RuntimeError: Expected object of type torch.FloatTensor but found type torch.cuda.FloatTensor for argument
Python
0 vote226 views1 answer
Np.split dataframe specific conditionm
Python