This is not a bug, it is normal handling of `and` and `or` operators since Python 1.5 and possibly older.

The `and` and `or` operators are *short-cut* operators. This is intentional design, so we can write things like:

    if mylist and mylist[0] == value:

the `mylist[0] == value` expression is only evaluated if `mylist` is a truthy value.

This is all documented here:

https://docs.python.org/3/reference/expressions.html#boolean-operations