学习资源：廖雪峰Python教程——切片
牢记：代码越少越好，逻辑越简单越好
尝试了3种实现方法，其中trim1是类C的实现，逻辑复杂，trim2和trim都是pythonic的，但是trim巧妙地解决了空字符串地情况，代码更加少、更加简洁。
#!/usr/bin/env python3
# -*- coding: utf-8 -*-def trim1(s):idx=-1for ss in s: #去除首部空格if(ss==' '):idx += 1 #最后一个空格所在的下标else:s=s[idx+1:]breakridx=0count=0for ss in s:if(ss==' '):count += 1continueelse:ridx += 1+count #最后一个非空格字符的下一个下标count=0s=s[:ridx]return sdef trim2(s):while((s != '') and (s[0]==' ')):s=s[1:]while(s != '' and s[-1]==' '):s=s[:-1]return sdef trim(s):while(s[:1]==' '): #即使空字符串也不会索引越界s=s[1:]while(s[-1:]==' '): #即使空字符串也不会索引越界s=s[:-1]return s#test
print("trim('hello ') =", trim('hello ') )
print("trim(' hello') =", trim(' hello') )
print("trim(' hello ') =", trim(' hello ') )
print("trim(' hello world ') =", trim(' hello world '))
print("trim('') =", trim('') )
print("trim(' ') =", trim(' ') )if trim('hello ') != 'hello':print('#1 测试失败!')
elif trim(' hello') != 'hello':print('#2 测试失败!')
elif trim(' hello ') != 'hello':print('#3 测试失败!')
elif trim(' hello world ') != 'hello world':print('#4 测试失败!')
elif trim('') != '':print('#5 测试失败!')
elif trim(' ') != '':print('#6 测试失败!')
else:print('测试成功!')
测试结果：
C:\python>trim.py
trim('hello ') = hello
trim(' hello') = hello
trim(' hello ') = hello
trim(' hello world ') = hello world
trim('') =
trim(' ') =
测试成功!