> On Sep 13, 2017, at 6:37 PM, Nick Coghlan <ncogh...@gmail.com> wrote: > > I think it would be useful for the PEP to include a definition of an > "eager annotations" decorator that did something like: > > def eager_annotations(f): > ns = f.__globals__ > annotations = f.__annotations__ > for k, v in annotations.items(): > annotations[k] = eval(v, ns) > return f > > And pointed out that you can create variants of that which also pass > in the locals() namespace (or use sys._getframes() to access it > dynamically). > > That way, during the "from __future__ import lazy_annotations" period, > folks will have clearer guidance on how to explicitly opt-in to eager > evaluation via function and class decorators.
I like this idea! For classes it would have to be a function that you call post
factum. The way class decorators are implemented, they cannot evaluate
annotations that contain forward references. For example:
class Tree:
left: Tree
right: Tree
def __init__(self, left: Tree, right: Tree):
self.left = left
self.right = right
This is true today, get_type_hints() called from within a class decorator will
fail on this class. However, a function performing postponed evaluation can do
this without issue. If a class decorator knew what name a class is about to
get, that would help. But that's a different PEP and I'm not writing that one
;-)
- Ł
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