If you use the technique more generally, you need to watch out for the first case: bool(0) -> False bool(1) -> True bool(str('0')) -> True bool(str('')

If you use the technique more generally, you need to watch out for the first case: bool(0) -> False bool(1) -> True bool(str('0')) -> True bool(str('')) -> False bool(None) -> False If you are checking that a variable is set bool(some_var) doesn't work for 0.