Any object can be tested for truth value, for use in an if or while condition or as operand of the Boolean operations below. The following values are considered false:
All other values are considered true -- so objects of many types are always true.
Operations and built-in functions that have a Boolean result always
0 for false and
1 for true, unless otherwise
stated. (Important exception: the Boolean operations
"or" and "and" always return one of