On Apr 4, 10:42 am, Gerardo Herzig <[EMAIL PROTECTED]> wrote:
> Hi all. [EMAIL PROTECTED] over here. Im missing some point here, but cant
> figure out which one.
>
> This little peace of code executes a 'select count(*)' over every table
> in a database, one thread per table:
> <code>
> class TableCounter(threading.Thread):
> def __init__(self, conn, table):
> self.connection = connection.Connection(host=conn.host,
> port=conn.port, user=conn.user, password='', base=conn.base)
> threading.Thread.__init__(self)
> self.table = table
>
> def run(self):
> result = self.connection.doQuery("select count(*) from %s" %
> self.table, [])[0][0]
> print result
> return result
>
> class DataChecker(metadata.Database):
>
> def countAll(self):
> for table in self.tables:
> t = TableCounter(self.connection, table.name)
> t.start()
> return
> </code>
>
> It works fine, in the sense that every run() method prints the correct
> value.
> But...I would like to store the result of t.start() in, say, a list. The
> thing is, t.start() returns None, so...what im i missing here?
> Its the desing wrong?
The simplest way is to just store it as an attribute in the
TableCounter instance:
def run(self):
self.result = self.connection.doQuery(...)
Another alternative is to add it to a Queue. You can't use a list
unless you protect with a lock to prevent concurrent append()s, but
that's what Queues do anyway [1].
Regardless of where the results are stored, a second issue which you
don't address here is, how do you know that a given result or all
results are done ? Again there are several alternatives, but Python
2.5 adds two convenient Queue methods for this, task_done() and
join(). Check out the example at the bottom of the Queue doc page [2]
to see how it works.
HTH,
George
[1] http://docs.python.org/lib/module-Queue.html
[2] http://docs.python.org/lib/QueueObjects.html
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