Hello, python world!
I'm looking for a way to implement a kind of "named" list, or named tree, with
the following requirements:
* Each item is named (or key-ed), like in a dict.
* Each item (node) can be either a terminal item (leaf) or a sub-list (branch).
* There may be items with the same name, unlike in a dict.
* The item entering order is preserved, unlike in a dict.
* A non-requirement: may be useful that items can be retrieved by name (in case
several items have the same name, it's allright to return first one -- it's up
to the client code to manage that)
A structural representation of such an object looks like that:
obj
n1:val
n2:val
n3
n31:val
n32
n321:val
n322:val
n33
n4
Which is exactly the same as for a list, except that each item gets a name in
addition to its value.
I ask for advices before doing bull**** as I suspect there may be a data
structure in language theory that matches that needs. Some questions:
* Do you know of such a structure?
* What is the difference between a tree and a python list? a tree and an array
that allows nesting?
* Are items in a tree, as defined in theory, supposed to be of homogeneous type?
I cannot implement that simply by giving items an additional attribute, for
items can be of an type and can even change. They also need a whole bunch of
custom methods. This would require sub-typing averu possible type, including
custom ones (this was the cause of a previous, in which I asked if it was
possible to sub-type at a type known at runtime). So I plan instead to
implement the whole load of necessary behaviour in a container, thus letting
the items unchanged.
A possible design (?) would be to subtype list in order to add such a container
object a parallel list of names. So that direct access still directly reaches
values, while matching names are accessed by indexing a parallel list:
obj[n] <-- item
obj.names[n] <-- name
And maybe:
obj.link[n] <-- (name,item)
obj[name] <-- item
obj.name(item) <-- name
Denis
------
la vida e estranya
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