In Python how should I test if a variable is None, True or False

Question

I have a function that can return one of three things:

• success (True)
• failure (False)
• error reading/parsing stream

Answer 1

There are many good answers. I would like to add one more point. A bug can get into your code if you are working with numerical values, and your answer is happened to be 0.

a = 0 
b = 10 
c = None

### Common approach that can cause a problem

if not a:
    print(f"Answer is not found. Answer is {str(a)}.") 
else:
    print(f"Answer is: {str(a)}.")

if not b:
    print(f"Answer is not found. Answer is {str(b)}.") 
else:
    print(f"Answer is: {str(b)}")

if not c:
    print(f"Answer is not found. Answer is {str(c)}.") 
else:
    print(f"Answer is: {str(c)}.")

Answer is not found. Answer is 0.   
Answer is: 10.   
Answer is not found. Answer is None.

### Safer approach 
if a is None:
    print(f"Answer is not found. Answer is {str(a)}.") 
else:
    print(f"Answer is: {str(a)}.")

if b is None:
    print(f"Answer is not found. Answer is {str(b)}.") 
else:
    print(f"Answer is: {str(b)}.")

if c is None:
    print(f"Answer is not found. Answer is {str(c)}.") 
else:
    print(f"Answer is: {str(c)}.")

Answer is: 0.
Answer is: 10.
Answer is not found. Answer is None.