用Python写一段实现剪切功能的程序。

#!/usr/bin/env python
#coding: utf8

import sys

mystr = []

def inputstr():
    item = raw_input("Please input your string:")
    mystr[:] = []     #清空列表
    mystr.extend(item)  #将输入的字符串拆开为一个一个字符填入列表

def printstr():
    lenth = len(mystr) - 1
    index = 0
    print "Your result is :"
    print "*****" + "".join(mystr) + "*****"
    #.join()与之前的extend对应，将字符合并为一个元素，用""里面的内容分割。""里面为空，则字符之间没有间隙
    print "----------------分割符----------------"

def leftstrip(): #左剪切
    while True:
        if mystr[0] == " ":
            mystr.pop(0)
        else:
            break
    printstr()

def rightstrip():#右剪切
    while True:
        if mystr[-1] == " ":
            mystr.pop()
        else:
            break
    printstr()

def bothsidestrip():
    while True:
        if mystr[-1] == " ":
            mystr.pop()
        elif mystr[0] == " ":
            mystr.pop(0)
        else:
            break
    printstr()
#使用字典的方式，实现case的语法功能
CMDs = {"l":leftstrip,"r":rightstrip,"b":bothsidestrip}

def showmenu():
    prompt = """(L)eftstrip
(R)ightstrip
(B)othsidestrip
(Q)uit
Please select a choice:"""
    while True:
        choice = raw_input(prompt).lower()
        if choice not in "lrbq":
            continue
        if choice == "q":
            break
        inputstr()
        CMDs[choice]()

if __name__=="__main__":
    showmenu()