[Tutor] OOPs?

[Kirby Urner]

At 08:27 AM 3/29/2002 -0600, Bryce Embry wrote:
>Howdy,
>I'm trying to get the hang of classes and would like to tap into the wealth
>of this tutorial for some guidance.

You could have a stock class and then stuff stock objects made
from it into a dictionary (similar to a stock list -- but just
for looking up by ticker code).

Here's a simple module, for pedagogical purposes only, as you
say (not to make a mint).

Note that I use a dictionary-like file to store my stock objects,
in order to gain persistence from one Python session to the next.

=============

import time, shelve

class Stock:
    "Simple stock class, keeps history using current time"

    def __init__(self,code,price,datetime):
        self.code = code
        self.history = [(price,datetime)]
        self.price = price

    def newprice(self,price,datetime):
        self.history.append((price,datetime))

    def showhist(self):
        return self.history

def getcode():
     "Handle cases where user inputs code we don't have"
     code  = raw_input("Code?  > ")
     try:
        stockobj = stockdict[code]
     except:
        print "Not a legal code"
        return 0
     return stockobj

def addstock():
     "Add new stock, any code OK"
     code  = raw_input("Code?  > ")
     price = raw_input("Price? > ")
     stockdict[code] = Stock(code,price,time.asctime())

def update():
     obj  = getcode()
     if obj:
         price = raw_input("Price? > ")
         obj.newprice(price,time.asctime())
         print "%s prices on file" % len(obj.history)
         # would have to do next step if using real dictionary
         stockdict[obj.code]=obj # overwrites old copy

def dumphist():
     obj  = getcode()
     if obj:
         hist = obj.showhist()
         print hist

def quit():
     stockdict.close()
     print "Stocks saved"

def mainmenu():
     "Using dictionary-like syntax to do file i/o"
     global stockdict
     stockdict = shelve.open("mystocks")
     callables = [quit,addstock,update,dumphist]
     while 1:
         print \
         """
         (1) add new stock
         (2) update price of stock
         (3) dump history of stock
         (0) save/quit
         """
         sel = raw_input("yr choice: > ")
         try:
            sel = int(sel)
            assert int(sel) <= 3 and int(sel) >= 0
            callables[int(sel)]()
            if int(sel)==0:  break
        except:
            print "Not a legal choice"

=============
Usage (in shell mode):

  >>> import stocks
  >>> stocks.mainmenu()

         (1) add new stock
         (2) update price of stock
         (3) dump history of stock
         (0) save/quit

  yr choice: > 1
  Code?  > CISCO
  Price? > 23.12

         (1) add new stock
         (2) update price of stock
         (3) dump history of stock
         (0) save/quit

  yr choice: > 3
  Code?  > IBM   [saved in an earlier session ]
  [('12.75', 'Fri Mar 29 09:40:45 2002'), ('12.10', 'Fri Mar 29 09:40:54 
2002'),
  ('45', 'Fri Mar 29 09:41:50 2002')]

         (1) add new stock
         (2) update price of stock
         (3) dump history of stock
         (0) save/quit

  yr choice: > 2
  Code?  > CISCO
  Price? > 14.10
  2 prices on file

         (1) add new stock
         (2) update price of stock
         (3) dump history of stock
         (0) save/quit

  yr choice: > 3
  Code?  > CISCO
  [('23.12', 'Fri Mar 29 09:44:16 2002'), ('14.10', 'Fri Mar 29 09:44:35 
2002')]

         (1) add new stock
         (2) update price of stock
         (3) dump history of stock
         (0) save/quit

  yr choice: > 0
  Stocks saved

Kirby