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 '\nYou 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', '']

 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']