python实现数据结构-栈

注：本文档主要是学习《Python核心编程(第二版)》时的练习题。

栈是一种"后进先出"的数据结构（LIFO），是一种操作受限的线性结构，数据只能从栈顶进入和栈顶出去。示意图如下：

 代码实现方式如下：

#!/usr/bin/env python

stack = []

def pushstack():
    stack.append(raw_input('Enter new string: '))

def popstack():
    if len(stack) == 0:
        print 'Cannot pop from empty stack!'
    else:
        print 'Removed [', stack.pop(), ']'

def viewstack():
    print stack

CMDs = {'u':pushstack, 'o':popstack, 'v':viewstack}

def showmenu():
    pr = """
p(U)sh
P(O)p
(V)iew
(Q)uit
Enter choice:"""

    while True:
        try:
            choice = raw_input(pr).strip()[0].lower()
        except(EOFError, keyboardInterrupt, IndexError):
            choice = 'q'

        print '
You picked: [%s]' % choice
        if choice not in 'uovq':
            print 'Invalid option, try again'
            continue

        if choice == 'q':
            break
        
        CMDs[choice]()


if __name__ == '__main__':
    showmenu()

测试现象：

[root@localhost python]# python stack.py 

p(U)sh
P(O)p
(V)iew
(Q)uit
Enter choice:u

You picked: [u]
Enter new string: abc

p(U)sh
P(O)p
(V)iew
(Q)uit
Enter choice:u

You picked: [u]
Enter new string: cde

p(U)sh
P(O)p
(V)iew
(Q)uit
Enter choice:u

You picked: [u]
Enter new string: 123

p(U)sh
P(O)p
(V)iew
(Q)uit
Enter choice:v

You picked: [v]
['abc', 'cde', '123']

p(U)sh
P(O)p
(V)iew
(Q)uit
Enter choice:o

You picked: [o]
Removed [ 123 ]

p(U)sh
P(O)p
(V)iew
(Q)uit
Enter choice:o

You picked: [o]
Removed [ cde ]

p(U)sh
P(O)p
(V)iew
(Q)uit
Enter choice:v

You picked: [v]
['abc']