python中返回true,为什么类型在Python中返回True？

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:

None

False

zero of any numeric type, for example, 0, 0L, 0.0, 0j.

any empty sequence, for example, '', (), [].

any empty mapping, for example, {}.

instances of user-defined classes, if the class defines a

__nonzero__() or __len__() method, when that method returns the integer zero or bool value False. [1]

> 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

return 0 or False for false and 1 or True for true, unless otherwise

stated. (Important exception: the Boolean operations or and and always

return one of their operands.)