考了最简单的编程题， 我记错了点， a,b 那个不会会报错：太多返回值， 方法只返回tuple或者解包
>>> def aa():
... return 1,2,3
...
>>> a = aa()
>>> print(a)
(1, 2, 3)
>>> a , b = aa()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: too many values to unpack (expected 2)
>>>
>>> a,b = aa()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: too many values to unpack (expected 2)
>>> a,b,c = aa()
>>> print(a,b,c)
1 2 3
>>>
