Organising data within a program

[James Stroud]

Python is an object oriented (OO) language. The very best thing if you have a 
lot of time is to learn the language fully, read several books on database 
design, and implement a gui driven app, OO from top to bottom.

If you need to get something to work before you have time to become a 
pythonologist, try an array of dictionaries (AoD), a datastructure I find 
very handy in a pinch. Here are some patterns for you to think about (also 
have some masochistic fun trying to do something similar in perl--now try in 
perl without pointers if you cheated!):

#
# my_aod.py : an aod example module
#

# top of your module
import pickle

# saving your database (3 steps recommended)
def my_save_aod(aod,filename):
  afile = open(filename,"w")
  pickle.dump(aod,afile)
  afile.close()

# load your database (3 steps recommended)
def my_load_aod(filename):
  afile = open(filename)
  an_aod = pickle.load(afile)
  afile.close()
  return an_aod

# get a subset whose records match the key
def my_aod_find(aod,akey,avalue):
  sub_aod = []
  for element in aod:
    if element[akey] == avalue:
      sub_aod.append(element)
  return sub_aod

# a simple key based sort
def my_aod_sort(aod,akey):
  return_aod = aod[:]
  return_aod.sort(lambda x,y : cmp(x[akey],y[akey]))
  return return_aod
#
# methinks a module hath I begun
#
# end my_aod.py



###########################################################
# example usage of an aod (new file)
#

from my_aod import *

# some records to start you off
bob = {"name":"Bob","spouse":"Carol","phone":"8675309"}
carol = {"name":"Ted","spouse":"Alice","phone":"5551212"}
ted = {"name":"Alice","spouse":"Ted","phone":"5551212"}
alice = {"name":"Carol","spouse":"Bob","phone":"8675309"}

# adding records arbitrarily
database = [bob]
database.extend([carol,ted])
database.append(alice)

# playing with find and sort
for person in my_aod_find(database,"name","Bob"):
   print "name:", person["name"], "; spouse:", person["spouse"]

for person in my_aod_sort(database,"name"):
   print "name:", person["name"]

for person in my_aod_sort(database,"spouse"):
   print "name:", person["name"], "; spouse:", person["spouse"]

my_save_aod(database,"people.pkl")

new_db = my_load_aod("people.pkl")

for person in new_db:
  print "name:", person["name"], "; spouse:", person["spouse"]





On Monday 13 December 2004 03:06 pm, Nick Evans wrote:
> Hey all,
> I am currently working on a simple program (small group membership
> database) just to get to grips with the language (bit of a newbie here :-))
> and am wondering about the best way of organising the data within the
> program.
>
> >From my understanding I would have something like person1
>
> =("name","address","phone","subs-due")
> Then you would put    membershipdatabase = (person1, person2, personX....)
> etc
> Now is this the best way of organising this data within the program or is
> there a better "known" way?
>
> Also I want to just store this info to a standard txt file. Probably CSV or
> something. Is there any particular way I should be saving this data to
> file?
>
>
> Thanks in advance
>
> Nick

-- 
James Stroud, Ph.D.
UCLA-DOE Institute for Genomics and Proteomics
611 Charles E. Young Dr. S.
MBI 205, UCLA 951570
Los Angeles CA 90095-1570
http://www.jamesstroud.com/