Question

I’m implementing a Fenwick tree class in python.

Basically I have an internal list and two methods, get(key) and increase(key, inc), to handle reading and updating this list.
Mapping f[5] to f.get(5) is easy with __getitem__, but is there any way to make f[5] += 2 mean f.increase(5, 2)?

I found a relevant mailing list thread that says it can’t be done unless you wrap the results from __getitem__ in a proxy-class that implements __iadd__, but that’s not an option. So I’ll probably have to accept that I’ll have to use the increase-method, just thought I’d ask here just in case some genius has the solution.

I’m using python3.2 by the way.

Answer 1

No, the approach you described is pretty much the only option. There may be minor variations, but there’s no (sane, at least) way around the fact that f[5] += 2 will call __getitem__, then __setitem__, and do the + part only on the object retrieved, without considering the container.