def trim(s):
i=0
k=len(s)
if k==0:
return s
while i<k and s[i]==' ':
i=i+1
if i==k:
return s[i:]
while s[k-1]==' ':
k=k-1
s=s[i:k]
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!')