Ah, brilliant! So now I'm analyzing what prevented me from coming up with that solution before.... it looks like my problem, or mental block, was that I was trying to find a magic incantation to allow me to get the whole dict-of-set behavior defined from the A class, rather than allowing it to be staged across A and B where it naturally fits. That is exactly where I should have seen that associationproxy would handle the rest, but I must have been attempting to use associationproxy in a different way. At some point I remember succumbing to a mental storm of infinite recursion and had to just put down the keyboard and back away slowly.
I'm excited to give this a test-drive. On Mar 13, 10:24 am, Michael Bayer <mike...@zzzcomputing.com> wrote: > its probably easier to use __missing__ - see attached. > > dict_of_sets_with_default.py > 1KViewDownload > > > > On Mar 13, 2011, at 4:26 AM, Eric Ongerth wrote: > > > Thank you, Mike. Hmm... I tried exactly that technique, the last time > > I found myself with a similar need, a year or two ago. I seem to > > remember it only caused the problem to regress one step farther. But > > I must have missed something and will probably give it another shot. > > > Any suggestions on how to replace the dict in one of these situations > > with a defaultdict? Just override __setitem__ and __getitem__ ? > > > - Eric > > > On Mar 12, 10:26 pm, Michael Bayer <mike...@zzzcomputing.com> wrote: > >> On Mar 10, 2011, at 6:20 PM, Eric Ongerth wrote: > > >>> So, jek, if you're listening, or anyone else -- is there an already > >>> existing, working implementation of a Dict of Lists or Dict of Sets > >>> collection class? > > >> the association_proxy is always there to flatten the "object" in the > >> middle of two relationships typically along an association - so just > >> A->relationship->dict of B->relationship->set of C, association proxy from > >> A to B.cs. > > >>> On Mar 10, 1:55 pm, Eric Ongerth <ericonge...@gmail.com> wrote: > >>>> Ach, I did it again... proceeded as if column_mapped_collection and > >>>> attribute_mapped_collection provide collection classes that are dicts > >>>> of lists. No, they're just dicts of scalar values! > > >>>> Again and again I need dicts of lists. They seem to really fit the > >>>> data that I tend to work with; A's related to C's indexed by B's (the > >>>> B typically indicating the *type* of relationship between the A and > >>>> the C). > > >>>> Eventually I need to work my own implementation of dict-of-lists and > >>>> dict-of-dicts collection classes up to full strength so I can share > >>>> them as a recipe or extension or something. > > >>>> On Mar 10, 1:02 pm, Eric Ongerth <ericonge...@gmail.com> wrote: > > >>>>> I make occasional use of alternate collection classes for my > >>>>> sqlalchemy relationships. For example, column_mapped_collection. The > >>>>> existing collection classes in sqlalchemy.orm.collections work really > >>>>> well for me; I have a lot of relational data that very naturally > >>>>> belongs in dicts rather than lists because it makes sense as one thing > >>>>> indexed or mapped by another. > > >>>>> I find that I often need to add an item to one of these dict-mapped > >>>>> collections and would rather not have to check whether the key already > >>>>> exists in the dict. So I'm doing, essentially: > >>>>> collection.setdefault(key, []).append(value). > > >>>>> As a matter of syntactic sugar (which alternative collection classes > >>>>> already are, anyway) I would like to have collection classes backed by > >>>>> dicts with the capability of python's defaultdict, so that I could > >>>>> write more simply, and with equivalent results: > >>>>> collection[key].append(value) > > >>>>> I understand how to create my own collection class which will behave > >>>>> as desired. My question is, has anyone already got code for this that > >>>>> I could borrow rather than reinvent the wheel? Thanks in advance. -- > >>>>> Eric > > >>> -- > >>> You received this message because you are subscribed to the Google Groups > >>> "sqlalchemy" group. > >>> To post to this group, send email to sqlalchemy@googlegroups.com. > >>> To unsubscribe from this group, send email to > >>> sqlalchemy+unsubscr...@googlegroups.com. > >>> For more options, visit this group > >>> athttp://groups.google.com/group/sqlalchemy?hl=en. > > > -- > > You received this message because you are subscribed to the Google Groups > > "sqlalchemy" group. > > To post to this group, send email to sqlalchemy@googlegroups.com. > > To unsubscribe from this group, send email to > > sqlalchemy+unsubscr...@googlegroups.com. > > For more options, visit this group > > athttp://groups.google.com/group/sqlalchemy?hl=en. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
