newbie file/DB processing

[Magnus Lycka]

len wrote:
> I am an old time
> cobol programmer from the IBM 360/370 eria and this ingrained idea of
> file processing using file definition (FD's) I believe  is causing me
> problems because I think python requires a different way of looking at
> datafiles and I haven't really gotten my brain around it yet. 

Yup, Python uses the same world view as C, C++, Unix etc.

> I would
> like to create a small sequential file, processing at first to store a
> group id, name, amount, and date which I can add to delete from and
> update. Could someone point me to some code that would show me how this
> is done in python.  Eventually, I intend to expand my little program to
> process this file as a flat comma delimited file, move it to some type
> of indexed file and finally to some RDBMS system.  My little program
> started out at about 9 lines of code and is now at about 100 with 5 or
> six functions which I will eventually change to classes (I need to
> learn OOP to but one step at a time).

I think it's much easier to go directly to SQL without those
diversions. In a way, an SQL database maps better to your idea
of files / records, and it just takes much less code and effort
to use SQL than to twist "normal" (for me) files into behaving
like main frame dittos.

I'd suggest that you download pysqlite. Then you have a small
embedded SQL database in your python program and don't need to
bother with a server. See http://initd.org/tracker/pysqlite

Another obvious solution, since you are saying that it's a
small file, is to always read the whole file into memory, and
to rewrite the whole file when you change things.

For info in CSV handling, see http://docs.python.org/lib/module-csv.html

For other non-SQL solutions, please have a look at
http://www-106.ibm.com/developerworks/library/l-pypers.html
and http://docs.python.org/lib/node77.html