On 31May2016 04:57, Joshua Morton <joshua.morton13@gmail.com> wrote:
I like the arrow idea, another option is a syntax more in line with the one being discussed for dict unpacking, something like adding a __define__ dunder that returns a tuple of (name, value). So that say, Typevar's __define__ returns the tuple `(self.__name__, self)`. Which is then converted into an assignment. The downside of this being that its assignment overloading(which can be abused), but at least it can only be done when specifically asked for. The other downside is that the syntax
define TypeVar('T') # and I assume we can also declare a list of them def ident(t: T) -> T: return t [...] The upside is that it avoids the problem of Steven's implementation, since the name is decided internally by the callable.
Which to me is a downside. A big downside. Ignoring "from blah import *", when I write a Python module I have complete control over the local names: from os.path import join from os.path import join as joinpath x = 3 def y(): All of these are only capable of defining names that I have typed literally into my code. If I understand Joshua's suggestion: define TypeVar('T') might define _any_ name, because the __define__ dunder can return any name. Maybe I misunderstand, but otherwise I think this is like a little landmine. Yes, code can monkey patch. But this feels more insidious. Why not require the __dunder__ to always return __name__? And then perhaps support both: define TypeVar('T') define TypeVar('T') as Not_T so that providing the local name (which we're trying to avoid needing to do) _is_ possible, as the special case as it is with import. Cheers, Cameron Simpson <cs@zip.com.au>