I must be pedantic and separate the definition of "metaprogramming," and "dynamic programming;" of which this is the latter.

The reason this difference is important is that metaprogramming is structured and explicitly defines the change in the program's semantics.

Thankfully I have never seen code like what was posted in my experience with Python so far. Explicit is better than implicit which the code example in this post would fail to pass IMO. Dynamically dispatching to names that don't exist in a class' published interface at call-time is a big no-no in my book.

Although practicality beats purity.

I haven't seen it yet but that doesn't mean there is a practical reason to use this method of dynamic dispatch. If there were one and it gets a problem solved NOW rather than waiting to find a better solution -- it might be worthwhile.

However it's a price you have to pay.

I think the grep-test is at least a good way to test the waters with a bit of code. I don't think it's a universal end-all-discussions rule.