On 13 May 2018 at 20:00, Tim Peters <tim.pet...@gmail.com> wrote: > [Tim] > >> - If the target is not local to any function enclosing F, and is not > >> declared `global` in the block containing F, then the target is bound > >> in the block containing F. > > [also Tim] > > FYI, that's still not right, ... > > I suspect that the above should be reworded to the simpler: > > > > - If the target is not declared `global` or `nonlocal` in the block > > containing F, then the target is bound in the block containing F. > > ... > > I'm satisfied that captures the intent - but now it's misleadingly > wordy. It should be the briefer: > > - The target is bound in the block containing F. > > Other text (in section 4.2.2) already covers the intended meanings for > when a `global` or `nonlocal` declaration appears in the block too. > > And then it's short enough again that the bullet list isn't really > helpful anymore. So, putting that all together: > > """ > An assignment expression binds the target, except in a function F > synthesized to implement a list comprehension or generator expression > (see XXX). In the latter case[1], the target is bound in the block > containing F, and errors may be detected: If the target also appears > as an identifier target of a `for` loop header in F, a `SyntaxError` > exception is raised. If the block containing F is a class block, a > `SyntaxError` exception is raised. > > Footnote: > [1] The intent is that runtime binding of the target occurs as if the > binding were performed in the block containing F. Because that > necessarily makes the target not local in F, it's an error if the > target also appears in a `for` loop header, which is a local binding > for the same target. If the containing block is a class block, F has > no access to that block's scope, so it doesn't make sense to consider > the containing block. The target is bound in the containing block, > where it inherits that block's `global` or `nonlocal` declaration if > one exists, else establishes that the target is local to that block. > """ >
This is getting pretty close to being precise enough to be at least potentially implementable (thanks!), but there are still two cases that would need to be covered: - what happens inside a lambda expression? - what happens inside another comprehension or generator expression? Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia
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