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：
1 #!/usr/bin/env python 2 3 queue = [] 4 5 def enQ(): 6 queue.append(raw_input('Enter new string: ').strip()) 7 8 def deQ(): 9 if len(queue) == 0: 10 print 'Cannot pop from an empty queue!' 11 else: 12 print 'Remove [', queue.pop(0), ']' 13 14 def viewQ(): 15 print queue 16 17 CMDs = {'e':enQ, 'd':deQ, 'v':viewQ} 18 19 def showmenu(): 20 pr = """ 21 (E)nqueue 22 (D)equeue 23 (V)iew 24 (Q)uit 25 26 Enter choice: """ 27 28 while True: 29 try: 30 choice = raw_input(pr).strip()[0].lower() 31 except (EOFError, keyboardInterrupt, IndexError): 32 choice = 'q' 33 34 print ' Your picked: [%s]' % choice 35 36 if choice == 'q': 37 break 38 elif choice not in 'dev': 39 print 'Invalid option, try again' 40 else: 41 CMDs[choice]() 42 43 if __name__ == '__main__': 44 showmenu()
测试现象：
1 [root@localhost python]# python queue.py 2 3 (E)nqueue 4 (D)equeue 5 (V)iew 6 (Q)uit 7 8 Enter choice: e 9 10 Your picked: [e] 11 Enter new string: abcd 12 13 (E)nqueue 14 (D)equeue 15 (V)iew 16 (Q)uit 17 18 Enter choice: e 19 20 Your picked: [e] 21 Enter new string: 1234 22 23 (E)nqueue 24 (D)equeue 25 (V)iew 26 (Q)uit 27 28 Enter choice: v 29 30 Your picked: [v] 31 ['abcd', '1234'] 32 33 (E)nqueue 34 (D)equeue 35 (V)iew 36 (Q)uit 37 38 Enter choice: d 39 40 Your picked: [d] 41 Remove [ abcd ] 42 43 (E)nqueue 44 (D)equeue 45 (V)iew 46 (Q)uit 47 48 Enter choice: v 49 50 Your picked: [v] 51 ['1234'] 52 53 (E)nqueue 54 (D)equeue 55 (V)iew 56 (Q)uit