# -*- coding: utf-8 -*- def trim(s): if len(s)==0: return '' if s[:1]==' ': return trim(s[1:]) elif s[-1:]=='': return trim(s[:-1]) else: return s
# 测试: if trim('hello ') != 'hello': print('测试失败!') elif trim(' hello') != 'hello': print('测试失败!') elif trim(' hello ') != 'hello': print('测试失败!') elif trim(' hello world ') != 'hello world': print('测试失败!') elif trim('') != '': print('测试失败!') elif trim(' ') != '': print('测试失败!') else: print('测试成功!')