def trim(s):

    i = 1

    j = -1

    if len(s) != 0:

        while s[:i] == ' ':

            s = s[i:]

        while s[j:] == ' ':

            s = s[:j]

        return s

    else:

        return s

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!')