学习笔记之Python 切片：利用切片操作，实现一个trim()函数，去除字符串首尾的空格

需求： 
Python 切片：利用切片操作，实现一个trim()函数，去除字符串首尾的空格，不调用str的strip()方法。# Basic Version:
def trim(s):
length = len(s)

if length > 0:
for i in range(length):
if s[i] != ' ':
break;
j = length-1;
while s[j] == ' ' and j >= i:
j -= 1
s = s[i:j+1]

return s

# Improvement Recursion
def trim(s):
if s[:1] != ' ' and s[-1:] != ' ':
return s
elif s[:1] == ' ':
return trim(s[1:])
else:
return trim(s[:-1])

# Test:
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!')转载自：http://blog.csdn.net/Daniel960601/article/details/79174915