python实现数据结构-队列

注：本文档主要是学习《Python核心编程(第二版)》时的练习题。

队列是一种"先进先出"的数据结构（FIFO），是一种操作受限的线性结构，先进队列的成员先出队列。示意图如下：

代码如下：

 #!/usr/bin/env python

 queue = []

 def enQ():
     queue.append(raw_input('Enter new string: ').strip())

 def deQ():
     if len(queue) == 0:
         print 'Cannot pop from an empty queue!'
     else:
         print 'Remove [', queue.pop(0), ']'

 def viewQ():
     print queue

 CMDs = {'e':enQ, 'd':deQ, 'v':viewQ}

 def showmenu():
     pr = """
 (E)nqueue
 (D)equeue
 (V)iew
 (Q)uit

 Enter choice: """

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

         print '\nYour picked: [%s]' % choice

         if choice == 'q':
             break
         elif choice not in 'dev':
             print 'Invalid option, try again'
         else:
             CMDs[choice]()

 if __name__ == '__main__':
     showmenu()

测试现象：

 [root@localhost python]# python queue.py    

 (E)nqueue
 (D)equeue
 (V)iew
 (Q)uit

 Enter choice: e

 Your picked: [e]
 Enter new string: abcd

 (E)nqueue
 (D)equeue
 (V)iew
 (Q)uit

 Enter choice: e

 Your picked: [e]
 Enter new string: 1234

 (E)nqueue
 (D)equeue
 (V)iew
 (Q)uit

 Enter choice: v

 Your picked: [v]
 ['abcd', '']

 (E)nqueue
 (D)equeue
 (V)iew
 (Q)uit

 Enter choice: d

 Your picked: [d]
 Remove [ abcd ]

 (E)nqueue
 (D)equeue
 (V)iew
 (Q)uit

 Enter choice: v

 Your picked: [v]
 ['']

 (E)nqueue
 (D)equeue
 (V)iew
 (Q)uit