python中除了if...elif...else..还有while...else, for...else..., try...except...else...finally...
不管哪种else, 其语义都是: 语句块的结尾, 如果语句块中间发生break,continue, return,或者异常, 则会直接跳出语句块, 换言之, else语句只有正常结束的时候才会执行, 如果if...elif...else中间已有匹配, while...else中间执行break, try...except..else...finally中间发生异常, 就不是正常结束, 也就不会执行else语句了.