def trim(str):
res = ''
con = len(str)
if con == 0:
return res
else:
front = 0
behind = 0
while front < con:
if str[front] == ' ':
front += 1
else:
break
if front == con:
return ''
while behind < con:
if str[con - behind - 1] == ' ':
behind += 1
else:
break
if behind == 0:
return str[front:]
else:
return str[front:-(behind)]
松霜杨雪
def trim(str): res = '' con = len(str) if con == 0: return res else: front = 0 behind = 0 while front < con: if str[front] == ' ': front += 1 else: break if front == con: return '' while behind < con: if str[con - behind - 1] == ' ': behind += 1 else: break if behind == 0: return str[front:] else: return str[front:-(behind)]