Python check for NoneType not working

python if-statement nonetype
Alex Blundell picture Alex Blundell · Dec 5, 2013 · Viewed 38.5k times · Source

I'm trying to check whether an object has a None type before checking it's length. For this, I've done an if statement with an or operator:

if (cts is None) | (len(cts) == 0):
return

As far as I can tell, the object cts will be checked if it's None, and if it is, the length check won't run. However, the following error happens if cts is None:

TypeError: object of type 'NoneType' has no len()

Does python check both expressions in an if statement, even if the first is true?

Answer

user2555451 picture user2555451 · Dec 5, 2013

In Python, | is a bitwise or. You want to use a logical or here:

if (cts is None) or (len(cts) == 0):
    return

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