Python－实现trim函数

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

def trim(s):
    if s[:1] == ' ':
        return trim(s[1:])
    if s[-1:] == ' ':
        return trim(s[:-1])
    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!')