newbie file/DB processing

[Paul Watson]

"len" <lsumnler at gmail.com> wrote in message 
news:1116445969.381550.99280 at f14g2000cwb.googlegroups.com...
> 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.

Welcome, Len.

> 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

In addition to the suggestions already given, you might take a look at the 
struct module.  This will let you use fixed-width binary records.

The concept of streams found in UNIX takes some getting used to.  Many files 
are maintained as text using delimited, variable length fields with a 
newline at the end.  Try 'cat /etc/passwd' on a UNIX/Linux host to see such 
a file using a colon ':' as the delimiter.

I turn to the 'od' command when I want the truth.  Use it to see what bytes 
are -really- in the file.  The following should work on Linux or under 
Cygwin if you are still using Windows.

    od -Ax -tcx1 thefile.dat

You can use od to look at data in the stream.  The output of the print 
command is going into the od command.

$ print "now"|od -Ax -tcx1
000000 6e 6f 77 0a
         n   o   w  \n
       6e 6f 77 0a
000004