Question about a design pattern in Chapter 18

[justinblaber]

Maybe not the best forum to ask this, but I have a question about this part in the AVL tree section:

def put(self, key, value):
    newroot = BalancedBSTNode.put(self, key, value)
    update(newroot)
    return newroot.rebalance()

I've never seen this design pattern before... is this called something? Like "recursive inheritance"? I think it's awesome and also a little mind bending. I would have never thought about extending recursive methods like this...

[donsheehy]

I sometimes think it should be called something like "Bad Code". Mind bending is really not good. I think it might be better to have another name for the basic insertion, inherit that, and call it. The reason is that it makes a lot of assumptions about the BalancedBSTNode.put implementation. If the name of the method were something like vanillaput, then we have some clear expectation that it doesn't do anything fancy. Then, some well-meaning programmer deciding to optimize put in the base class won't accidentally break the subclasses.