[Twisted-Python] Idiom for database access within iterator/generator?

[Maarten ter Huurne]

On Tuesday 03 June 2008, Justin Warren wrote:

> for item in generator_that_fetches_rows_from_database:
> 	...
> 	do_stuff()
> 	...
>
> where generator_that_fetches_rows_from_database is an object that uses
> enterprise.adbapi (or anything else) to fetch rows from a database and
> return them to the for..in.. loop.

I think decorating the method with @defer.inlineCallbacks and code like this 
might do the trick:

for d in generator_that_fetches_rows_from_database:
	try:
		row = yield d
	except SomeError:
		...
	else:
		do_stuff(row)

Depending on how you want to handle errors, you could put the "try" 
statement outside the loop.

The generator_that_fetches_rows_from_database does not yield actual rows, 
but a sequence of Deferreds, each of which delivers one row in its 
callback.

This is all untested, so it might contain a fatal flaw, but I hope it's 
useful.

Bye,
		Maarten
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