python空元组在all中返回结果详解

> all(2) #传入数值报错
Traceback (most recent call last):
 File "<pyshell#9>", line 1, in <module>
  all(2)
TypeError: 'int' object is not iterable

> all([1,2]) #列表中每个元素逻辑值均为True，返回True
True
> all([0,1,2]) #列表中0的逻辑值为False，返回False
False

> all(()) #空元组
True
> all({}) #空字典
True

all(iterable) # iterable -- 元组或列表。

> any(())
False
> any([])
False
> any(['',0])
False
> any(['',0,'1'])
True
> any(['',0,False])
False

def nontest():
 return None

x,y = nontest()

Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: 'NoneType' object is not iterable

try:
  x,y = nontest()
except TypeError:
  # do the None-thing here or pass

res = nontest()
if res is None:
  ....
else:
  x, y = res