On Fri, May 6, 2011 at 8:27 PM, Antoine Pitrou <solip...@pitrou.net> wrote: > On Fri, 06 May 2011 13:28:11 +1200 > Greg Ewing <greg.ew...@canterbury.ac.nz> wrote: > >> Amaury Forgeot d'Arc wrote [concerning the Doc/data/refcounts.dat file]: >> >> > This is not always true, for example when the item is already present >> > in the dict. >> > It's not important to know what the function does to the object, >> > Only the action on the reference is relevant. >> >> Yes, that's the whole point. When using a functon, >> what you need to know is whether it borrows or steals >> a reference. > > Doesn't "borrow" mean the same as "steal" in that context? > If an API borrows a reference, I expect it to take it from me.
Input parameter, borrowed or new reference: caller retains ownership and must still decref item Input parameter, stolen reference: caller transfers ownership and must NOT decref item (or must incref before call to guarantee lifecycle if planning to continue using the object after the call) Output parameter or return value, borrowed reference: caller does NOT receive ownership and does not need to decref item, but needs to be careful of lifecycle (and promote to a full reference with incref if the borrowed reference may outlive the original) Output parameter or return value, stolen or new reference: caller receives ownership and must decref item One interesting aspect is that from the caller's point of view, a *new* reference to the relevant behaves like a borrowed reference for input parameters, but like a stolen reference for output parameters and return values. It is typically the converse cases (stolen reference to an input parameter, borrowed reference to an output parameter or return value) that requires special attention on the caller's part. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
