[Tutor] Function problem

[Bob Gailer]

At 11:35 AM 11/5/2004, Eri Mendz wrote:
>Hello All,
>
>First off, thanks again to all who answered my loop problem Re: 
>'IndexError....'. I got it understood now.
>
>The problem of my script below is in the proceed function: if Y is
>selected, instead of staying in the option menu, the program just shows 
>the option menu then exits. ditto in the 'really quit program' prompt: i 
>expect to go to main menu if i select N but again program exits. can you 
>guys point me to my error? this is just a simple script but it took me 
>some time to figure out on my own; its a good learning exercise nevertheless.
>
>what to do to improve the program further, e.g., make it simple but
>efficient? i love to hear your good advise.
>
>#!/usr/bin/env python
># filename: tempConvert.py
># description: temperature conversion program
># Author: Eri Mendz
># Fri Nov  5 13:53:16 AST 2004
>
>import sys
>
>def print_options():
>     print '''
>     THIS IS A TEMPERATURE CONVERSION PROGRAM.
>     Options:
>     [C] - convert to Celsius
>     [F] - convert to Fahrenheit
>     [P] - print options
>     [Q] - quit
>     '''
>print_options()
>
>def f2c(ctemp):
>     return (9/5.0)*ctemp + 32
>
>def c2f(ftemp):
>     return (ftemp - 32) * 5/9.0
>
>def proceed():
>     proceed = raw_input("do another conversion? [Y|N]: ")
>     if proceed == 'y' or proceed =='Y':
>         print_options()
>     else:
>         confirmQuit()
>
>def confirmQuit():
>     ask = raw_input("Really quit program? [Y|N]: ")
>     if ask == 'y' or ask == 'Y' or ask == 'ye' or ask == 'yes':
>         sys.exit("bye")
>     else:
>         print_options()
>
># begin
>while 1:
>     choice = raw_input("select options: ")
>     if choice == 'c' or choice == 'C':
>         try:
>             getftemp = int(raw_input("enter fahrenheit temperature: "))
>             print "temp in C is: ", c2f(getftemp)
>             proceed()
>         except ValueError:
>             print "error: not a valid input!"
>         break
>     elif choice == 'f' or choice == 'F':
>         try:
>             getctemp = int(raw_input("enter centigrade temperature: "))
>             print "temp in F is: ", f2c(getctemp)
>             proceed()
>         except ValueError:
>             print "error: not a valid input!"
>         break
>     elif choice =='p' or choice == 'P':
>         print_options()
>     elif choice =='q' or choice == 'Q':
>         confirmQuit()
>     else:
>         print "invalid option"
>
>print "bye"

Since I enjoy OOP I thought I'd see what your program might look like using 
classes. Here's a cut at it:

import sys
class Menu:
   input_prompt = ''
   def prompt(self):
     print '[%s] - %s' % (self.__class__.__name__, self.menu_prompt)
   def act(self):
     if self.input_prompt:
       try:
         inp = raw_input(self.input_prompt)
         self.act_on_input(inp)
       except KeyboardInterrupt:
         pass

class Numeric(Menu):
   def act_on_input(self, inp):
     try:
       inp = int(inp)
       print self.output_prompt % self.convert(inp)
     except ValueError:
       print 'Input must be numeric.'

class Character(Menu):
   pass

class C(Numeric):
   menu_prompt = 'convert to Celsius'
   input_prompt = 'enter fahrenheit temperature: '
   output_prompt = 'temp in C is %s'
   def convert(self, ctemp):
     return (9/5.0)*ctemp + 32

class F(Numeric):
   menu_prompt = 'convert to Fahrenheit'
   input_prompt = 'enter centigrade temperature: '
   output_prompt = 'temp in F is %s'
   def convert(self, ftemp):
     return (ftemp - 32) * 5/9.0

class P(Character):
   menu_prompt = 'print options'
   def act_on_input(self, inp):
     print_options()

class Q(Character):
   menu_prompt = 'quit'
   input_prompt = 'Really quit program? [Y|N]: '
   def act_on_input(self, inp):
     if 'YES'.startswith(inp.upper()):
       sys.exit("bye")
     else:
       print_options()

menu = [C(), F(), P(), Q()]

def print_options():
     print '''
     THIS IS A TEMPERATURE CONVERSION PROGRAM.
     Options:    '''
     for item in menu:
       item.prompt()

print_options()
while 1:
   choice = raw_input("select option: ").upper()
   for item in menu:
     if item.__class__.__name__ == choice:
       item.act()
       break
   else:
     print "invalid option"
print "bye"

What I like about this is that all the information for a choice is packaged 
in the class definition, and there is minimal redundant code.

Bob Gailer
bgailer at alum.rpi.edu
303 442 2625 home
720 938 2625 cell