On 05/25/2016 02:12 PM, Paul Moore wrote:
On 25 May 2016 at 17:08, Ethan Furman <ethan@stoneleaf.us> wrote:
Here's a real-world use-case: The main software app I support passes a `values` dict around like the plague. When doing interesting stuff I often unpack some of the values into local variables as that reads better, types better, and makes it easier to reason about the code (it's on 2.7 so for that I'll have to use Random's example).
So for me, unpacking a dict with friendly syntax would be useful, and unpacking four or five keys from a 20-element dict will be far more useful than having to unpack them all.
Thanks. That's the sort of use case I thought might exist - and it sounds to me as if you'd get much more benefit from a syntax that allowed "partial" unpacking:
{"a": x, "b": y} = dict(a=1, b=2, c=3)
gives x=1, y=2 with no error.
I can't think of a good example where Michael's original proposal that this would give a ValueError would be a better approach. Paul
How is this an improvement over: def extract(mapping, *keys): return [mapping[key] for key in keys] mapping = {'a': 1, 'b': 2, 'c': 3} x, y = extract(mapping, 'a', 'b') print(x, y) 1, 2 Eric.