#!/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)

x = 10,y = 20
x = 20,y = 10