id	summary	reporter	owner	description	type	status	priority	milestone	component	resolution	keywords	cc	branch	branch_author	launchpad_bug
5912	Explain `d, self.deferred = self.deferred, None` idiom	tom.prince	exarkun	"This common idiom should be explained.

{{{
if self.deferred is not None:
     d, self.deferred = self.deferred, None
}}}
That code sets d to self.deferred at the same time as setting self.deferred to None. That way, if the code is called again later, then self.deferred, the condition in the if evaluates to False. Also, it gets rid of the reference to the deferred, allow it and all its callbacks (including the captured closures) to be garbage collected."	enhancement	closed	normal		core	fixed	documentation		branches/deferred-reference-clearing-5912	exarkun