Python Learning path 15--list implementation stacks and queues

Stack

A stack is a last-in, first-out (LIFO) data structure. You can add an object to the stack by using the push operation, or you can return and delete the top object by using a pop operation.

The following is the code for the list emulation stack:

<span style= "FONT-SIZE:14PX;" >#!/usr/bin/env python ' stack.py create a stack ' stack = []def pushit (): Stack.append (Raw_input (' Enter New string: '). Strip ()) def popit (): If Len (stack) = = 0:print ' cannot pop from an empty stack! '  Else:print ' Remove [', Repr (Stack.pop ()), '] ' def viewstack ():p rint stackcmds = {' U ': pushit, ' o ':p opit, ' V ': viewstack}def ShowMenu ():p r = "Push<span style=" White-space:pre "></span> #u represent Pushpop<span style=" White-space:pre "></span> #o represent Popview<span style=" White-space:pre "></span> #v represent Viewquit<span style= "White-space:pre" ></span> #q represent quitenter choice: ' While True:while true:try: Choice = raw_input (pr). Strip () [0].lower () except (Eoferror, Keyboardinterrupt, indexerror): choice = ' q ' print ' \nyou Picked: [%s] '% choiceif choice not in ' uovq ':p rint ' Invalid option, try again ' else:breakif choice = = ' Q ': break; Cmds[choice] () if __name__ = = ' __main__ ': ShowMenu () </span>

Here is the result of the operation:

<span style= "FONT-SIZE:14PX;"                >[email protected]:~/python> python stack.py push pop view                Quit Enter choice:vyou picked: [v][] Push pop view                Quit Enter choice:pyou picked: [p]invalid option, try again push                Pop view quit Enter choice:uyou picked: [U]enter New String:one Push pop view quit Enter choice:uyou picked: [U]enter New string:two push pop view quit Enter choice                : Uyou picked: [U]enter New string:three push pop view quit        Enter choice:vyou picked: [v][' One ', ' both ', ' three '] push pop        View quit Enter choice:oyou picked: [O]remove [' three '] push                Pop view quit Enter choice:vyou picked: [v][' One ', ' both '] Push pop view quit Enter choice:pyou picked: [P]invali d option, try again push pop view quit Enter Ch                Oice:oyou picked: [O]remove [' both '] push pop view quit                Enter choice:vyou picked: [v][' one '] push pop view Quit Enter Choice: </span>

Queue

A queue is a first in, Out (FIFO) data structure

The following is the code for the list emulation queue:

<span style= "FONT-SIZE:14PX;"        >#!/usr/bin/env pythonqueue = []def EnQ (): Queue.append (' Enter New string: '). Raw_input ()) def strip ():        If Len (queue) = = 0:print ' cannot pop from an empty queue! ' Else:print ' Removed [', repr (queue.pop (0)), '] ' Def viewq (): Print queue #calls str () in Ternailycmds = {' E ': EnQ, ' d ': DeQ, ' V ': Viewq}def showmenu (): PR = ' </span> <span style= ' fon t-size:14px; " > (E) nqueue (D) equeue (V) iew (Q) uit Enter choice: "WHI Le true:while True:try:choice = raw_input (pr). stri P () [0].lower () except (Eoferror, Keyboardinterrupt, indexerror): Cho                       Ice = ' Q ' print ' \nyou picked: [%s] '% choice if choice not in ' Devq ':         print ' Invalid option, try Again ' else:break if choice = = ' Q ': Break Cmds[choice] () if __name__ = = ' __main__ ': sh Owmenu () </span>

here is the result of the operation:

<span style= "FONT-SIZE:14PX;"                >[email protected]:~/python> python queue.py (E) nqueue (D) equeue                (V) iew (Q) uit Enter choice:eyou picked: [E]enter New String:one (e) nqueue                (D) Equeue (V) iew (Q) uit Enter choice:eyou picked: [E]enter New String:two (E) Nqueue (D) equeue (V) iew (Q) uit Enter choice:eyou Picke D: [E]enter New String:three (e) nqueue (D) equeue (V) Iew (Q) UI                T Enter Choice:vyou picked: [v][' One ', ' both ', ' three '] (E) nqueue (D) equeue                (V) iew (Q) uit Enter choice:dyou picked: [d]removed [' One '] (E) nqueue (D) Equeue (V) iew (Q) uit Enter choice:vyou picked: [v][', ' three '] (E) nqueue (D) equeue (V) iew (Q) uit Enter choice:dyou         Picked: [D]removed ['] (E) nqueue (d) equeue (V) iew (Q) uit                Enter choice:vyou picked: [v][' three '] (E) nqueue (D) equeue (v) iew (Q) uit Enter choice: </span>

Python Learning path 15--list implementation stacks and queues