strip

def mystrip(astring):
    alist = list(astring)
    list_len = len(alist)
    while alist[0] ==" ":
        del alist[0]
    while alist[len(alist) - 1] == " ":
        del alist[len(alist) - 1]
    print "".join(alist) #join 这是再往列表中添加什么？
bstring = raw_input('please input a string:')

mystrip(bstring)