On Aug 24, 2007, at 7:41 PM, Nathan Harmston wrote:
>
> Hi,
>
> I m trying to write a way of storing a 2 level dictionary in a
> database.
>
> class Foo(object):
> def __init__(self):
> self.a = {}
> def __iadd__(self, i):
> if i not in self.a:
> self.a[i] = {}
> return self
> def keys(self):
> for i in self.a.keys():
> yield i
> def __getitem__(self, k):
> return self.a[k]
> def save(self):
> # saves the object in the database
>
> f = Foo()
> f += Node1
> f[Node1][Node2] = edge
>
> THe idea is that its a self-referential join (node1 -> node2 ) with
> association object (edge), ie. node1 has many edges. one edge has has
> node1 and 1 node 2.
>
> IS there a pattern in sqlalchemy for doing this sort of thing, I
> noticed in the new version of SQLalchemy you can map to sets, but I m
> a little clueless where to start.
>
> Any help muchly appreciated.
the example examples/adjacencytree/basic_tree.py illustrates a self-
referential Node class which contains a map of child nodes. For a
pattern dealing with "edges" in the middle, theres an example
eaxmples/graph/graph.py .
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