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
False for false and
for true, unless otherwise stated. (Important exception: the Boolean
operations "or" and "and" always
return one of their operands.)