[Python-ideas] Proposal: Use mypy syntax for function annotations

[Stephen J. Turnbull]

Juancarlo Añez writes:

 > Reality is that most of the people most supportive of the migration
 > towards Python 3 are currently writing code that is compatible with
 > both 3.x and 2.[67].

And under Guido's proposal, they can continue to do so.  They just
have to live without the benefits of function annotations in that
code, same as they already do.  Or they can write a 3to2 tool to strip
the annotations.  It's just that the benefits to using Python 3 vs.
2/3-compatible syntax may take a quantum leap upward.  I don't see a
real problem here.

All that Guido is proposing to do is to rationalize development effort
on something people are already doing by standardizing a good-enough
approach, on an opt-in basis.  Sure, there are people who want
something more coercive, but Python developers aren't going to stand
for that, and Guido himself is the first line of defense.  He's
already said that's not going to happen, not now (and IIUC probably
never).