[转]在不声明新变量的情况下，让变量a和变量b的值互换？

>>> a = 1
>>> b = 9
>>> a = a + b
>>> b = a - b
>>> a = a - b
>>> a
9
>>> b
1

上面是转的，当时感觉思路挺不错。现在想想，在python中好像没必要这么麻烦：

>>>a =1
>>>b = 9
>>>a,b = b,a
>>>a
9
>>>b
1