题目：两个变量值互换。
程序分析：无
程序源代码：
实例
#!/usr/bin/python
# -*- coding: UTF-8 -*-
def exchange(a,b):
a,b = b,a
return (a,b)
if __name__ == '__main__':
x = 10
y = 20
print ('x = %d,y = %d' % (x,y))
x,y = exchange(x,y)
print ('x = %d,y = %d' % (x,y))
以上实例输出结果为：
x = 10,y = 20
x = 20,y = 10
