Python isdigit() and None

[GOTO10]

In circumstances like this where the value may be None (or an empty string, list, etc.), one option is to use and to make sure there is a value before trying isdigit().

So, instead of:

if presets.get('last').isdigit()

Do this:

if presets.get('last') and presets.get('last').isdigit()

This works because Python first evaluates if presets.get('last'). If there is no value, the condition is False (because False and x is False no matter what x is), so Python doesn't even evaluate beyond the "and".

Also, since the isdigit() method returns True or False, there is no need for the comparison operator:

if x.isdigit():  # accomplishes the same thing as if x.isdigit() == True: