用Python兑现栈

用Python实现栈

这是Python核心编程里的一个例子:

#!/usr/bin/env python#定义一个列表来模拟栈stack = []#进栈,调用列表的append()函数加到列表的末尾,strip()没有参数是去掉首尾的空格def pushit():    stack.append(raw_input('Enter new string: ').strip())#出栈,用到了pop()函数def popit():    if len(stack) == 0:        print 'Cannot pop from an empty stack!'    else:        print 'Removed [', stack.pop(), ']'#编历栈def viewstack():    print stack#CMDs是字典的使用CMDs = {'u': pushit, 'o': popit, 'v': viewstack}#pr为提示字符def showmenu():    pr = """    p(U)sh    p(O)p    (V)iew    (Q)uit        Enter choice: """    while True:        while True:            try:                #先用strip()去掉空格,再把第一个字符转换成小写的                choice = raw_input(pr).strip()[0].lower()            except (EOFError, KeyboardInterrupt, IndexError):                choice = 'q'            print '\nYou picked: [%s]' % choice            if choice not in 'uovq':                print 'Invalid option, try again'            else:                break#CMDs[]根据输入的choice从字典中对应相应的value,比如说输入u,从字典中得到value为pushit,执行pushit()进栈操作        if choice == 'q':            break        CMDs[choice]()#判断是否是从本文件进入,而不是被调用if __name__ == '__main__':    showmenu()