#!/usr/bin/env python

'''

$Id$

stack.py -- simulate stack data structures using lists

Exercises:

13-8) create a Stack class

13-10) create a class similar to arrays in Perl which have

both queue- and stack-like qualities and features

'''

# create our data structure

stack = []

#

# pushit() -- adds stirng to the stack

#

def pushit():

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

#

# popit() -- removes stirng from the stack

#

def popit():

if len(stack) == 0:

print 'Cannot pop from an empty stack!'

else:

print 'Removed [', stack.pop(), ']'

#

# viewstack() -- display stack contents

#

def viewstack():

print str(stack)

#

# showmenu() -- interactive portion of application

# displays menu to prompt user and takes

# action based on user response

#

def showmenu():

# using triple quotes to help us put together

# the multi-line string prompt to display

prompt = """

p(U)sh

p(O)p

(V)iew

(Q)uit

Enter choice: """

# loop until user quits

done = 0

while not done:

# loop until user choses valid option

chosen = 0

while not chosen:

# if user hits RETURN/Enter, ^C, or ^D (EOF),

# pretend they typed 'q' to quit normally

try:

choice = raw_input(prompt)[0]

except (IndexError, EOFError, KeyboardInterrupt):

choice = 'q'

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

# validate option chosen

if choice not in 'uovq':

print 'invalid option, try again'

else:

chosen = 1

# take appropriate action

if choice == 'q':

done = 1

if choice == 'u':

pushit()

if choice == 'o':

popit()

if choice == 'v':

viewstack()

# run showmenu() as the application

if __name__ == '__main__':

showmenu()