I am looking at the BTrees library and noticed that there are multiple TreeSet (and others) classes, e.g.
BTrees.IOBTree.TreeSetBTrees.OOBTree.TreeSetBTrees.LFBTree.TreeSetI understand that the BTree class is different for each one of these as it accepts different types for the keys and values, but how about the TreeSet class?
Though trial and error I found that the first letter dictates which types can be held by a TreeSet instance, but what about the second letter? Does it have any influence on how the members are stored/retrieved?
Is there any documentation on that?
No, the TreeSet classes ignore the second letter; they are provided in each XXBTree module for completeness and ease of importing.
Under the covers, the modules are created using a lot of creative preprocessor macro work, making it also just easier to produce a TreeSet type for each of the key-value type variants.
The package documentation relies in part on interface definitions; each module has an interface where the first sentence documents what the sets in that package contain:
class IIntegerObjectBTreeModule(IBTreeModule, IMerge):
"""keys, or set values, are integers; values are objects.
describes IOBTree and LOBTree"""
and
class IIntegerIntegerBTreeModule(IBTreeModule, IIMerge, IMergeIntegerKey):
"""keys, or set values, are integers; values are also integers.
describes IIBTree and LLBTree"""
for example illustrates that for both the IOBTree and IIBTree modules the set values are integers. As such, IOBTree.TreeSet and IIBTree.TreeSet are essentially the same.
The package documentation then uses those interface definitions to auto-generate the API docs, including the per-module documentation with the (tree)set value details.