Re: [Python-ideas] Spelling of Assignment Expressions PEP 572 (was post #4)
To me, "from" strongly suggests that an element is being obtained from a container/collection of elements. This is how I conceptualize "from module import name": "name" refers to an object INSIDE the module, not the module itself. If I saw
if (match from pattern.search(data)) is not None: ...
I would guess that it is equivalent to
m = next(pattern.search(data)) if m is not None: ...
+1, although unpacking seems to be reasonable `[elem1, *elems] from contains`. Now we have - "expr as name" - "name := expr" - "expr -> name" - "name from expr" Personally I prefer "as", but I think without a big change of python Grammar file, it's impossible to avoid parsing "with expr as name" into "with (expr as name)" because "expr as name" is actually an "expr". I have mentioned this in previous discussions and it seems it's better to warn you all again. I don't think people of Python-Dev are willing to implement a totally new Python compiler.
On 16 April 2018 at 00:27, Thautwarm Zhao
Personally I prefer "as", but I think without a big change of python Grammar file, it's impossible to avoid parsing "with expr as name" into "with (expr as name)" because "expr as name" is actually an "expr". I have mentioned this in previous discussions and it seems it's better to warn you all again. I don't think people of Python-Dev are willing to implement a totally new Python compiler.
We have ways of cheating a bit if we want to reinterpret the semantics of something that nevertheless parses cleanly - while the parser is limited to single token lookahead, it's straightforward for the subsequent code generation stage to look a single level down in the parse tree and see that the code that parsed as "with expr" is actually "with subexpr as target". So the main concern around "with (name as expr)" is with human readers getting confused, not the compiler, as we can tell the latter to implement whichever semantics we decide we want, while humans are far less tractable :) Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia
participants (2)
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Nick Coghlan -
Thautwarm Zhao