On 15/02/13 03:09, neubyr wrote:
I do have a doubt regarding this - e.g. how would I implement this if my
program/application is web based. For example, loading the text file
during web server start and stop.
For a long running process like a web server this is probably the wrong
approach. You probably want to save the data more regularly - maybe even
at the end of every user transaction. But with a web server we have the
additional problem of usually wanting to handle multiple requests in
parallel so storing data in memory gets more complicated - which takes
us back to using a data base which pretty much handles all of that for you.
If you will only have a single request running at a time then you can
use the same try/finally approach in your transaction processing code.
But because they run so often I'd add the 'dirty flag' idea that
somebody else mentioned too so that you don;t sabve if no changes have
been made.
A dirty flag is simply a global (or class) level variable (isDirty) that
gets set by your code anytime you change the data. If a book changes its
state it sets the flag to True. The save code then does something like
with open(filename) as store
if Book.isDirty:
for book in Book.instances:
book.save(store)
That will ensure that any changes are saved but we don't waste time
if no changes exist.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
