[Tutor] Generating unique ID

[Modulok]

> I'm writing an application which will hold a database of people. Ofcourse,
> people can have the same name, so I want to stock them with an unique ID.
>
> I've searched and found some things:
> - uuid.uuid4()
> - id(name)
> - os.urandom(n)
>
> But they seem overkill to me. Well, maybe not id().
>
> What should I use the best for this? Maybe examples of other programs that
> do something alike?

Use the auto-increment feature of your database database management
backend. (Assuming you're using a database backend like MySQL,
postgresql, etc.) In MySQL your database description would look
something like this (with any other fields  you need):

# MySQL table description:

CREATE TABLE IF NOT EXISTS mytable (
   `uid`    BIGINT unsigned NOT NULL auto_increment unique,
   `uname`  CHAR(32) NOT NULL default "guest",
PRIMARY KEY (`uid`));


You could use MySQLdb (third party python module) to talk to the MySQL
process with Python. Other database managers have similar abilities.

>> os.urandom(n)

Random numbers are random, NOT unique.

If you're using your own backend, like a text file or whatever, stop.
Take the time to learn to use a database manager like postgresql or
MySQL or whatever. They have already solved many of the problems
you're now facing. It will be well worth the time and frustration.

Otherwise, you'll have to parse your database and get the previously
used value and then increment that. However, this solution will fail
if there are multiple processes, or threads accessing the data
concurrently. To solve that problem you'll have to introduce some
manner of mutex to gurantee that only one process has access to the
unique data at any given time. Things get complicated. All of these
problems have already been solved with other database managers. Use
them!

In a pinch, with a low volume database for non-critical data, you
could probably get away with using a Unix epoch style timestamp with
sufficient granularity. But even this is in no way, "guaranteed" to be
unique. It's just, "probably unique". It would look like this:

>>> import time
>>> time.time()
1256796357.661967

If it absolutely must be unique, use a database manager that can make
that guarantee.

Best of luck!
-Modulok-