how to let argument be optional falling back to certain integer

[David Raymond]

> This is true.  I have written 0 as false in C so many times.  But
> clearly for me times have changed...  I now look at numbers as a thing
> in their own special class not to be confused as truth-values.  (So much
> so that I fell for this.)  But I confess I still think of numbers as all
> TRUE.  (Even zero!)


Also remember that in Python bool is a subclass of int:
>>> isinstance(False, int)
True
>>> 0 == False
True
>>> 1 == True
True
>>> ["A", "B"][False]
'A'
>>> ["A", "B"][True]
'B'

So if you're trying to do something slightly different based on the type of the input you might fall into this trap

if isinstance(foo, float):
    do float stuff
elif isinstance(foo, int):
    do int stuff
elif isinstance(foo, bool):
    this line will never run because it would have triggered the int line