Re: [Python-ideas] PEP: Dict addition and subtraction

Rhodri James wrote:

Making assumptions about length where any dictionary manipulations are concerned seems unwise to me

I think you're a bit hasty here. Some assumptions are sensible. Suppose

a = len(d1) b = len(d2) c = len(d1 + d2) # Using the suggested syntax.

Then we know max(a, b) <= c <= a + b

And this is, in broad terms, characteristic of merge operations.