[Python-ideas] Syntax idea: escaping names to avoid keyword ambiguity

Carl Smith carl.input at gmail.com
Mon May 14 17:25:59 EDT 2018

Sorry to think out loud, but if the lexer marked `foo` as a generic `Word`
token, that
could be a keyword or a name, then the parser could look at the value of
each `Word`
token, and if the context is `import foo`, `class foo...`, `def foo...` or
`foo = ...`,
then `foo` is a name there and thereafter (and `x foo y` is a SyntaxError)
you get the idea.

-- Carl Smith
carl.input at gmail.com

On 14 May 2018 at 22:06, Carl Smith <carl.input at gmail.com> wrote:

> Just to be clear, if `foo` was introduced as a new infix operator,
> projects that used `foo`
> as a name would not be able to also use `foo` as an infix operator in the
> file that defines
> `foo` as a name, but could use the operator throughout the rest of their
> project.
> -- Carl Smith
> carl.input at gmail.com
> On 14 May 2018 at 21:52, Carl Smith <carl.input at gmail.com> wrote:
>> I can only think of three ways to reference a name defined in a different
>> file: In an import
>> statement, as properties of objects and as keyword arguments.
>> Import statements are implicit assignments, so if Python allowed the
>> following grammar,
>> you could still import the odd thing that had a reserved name, without
>> bringing that name
>> into your local namespace.
>>     from <keyword> import <keyword> as <name>
>> Property names always follow a dot, where only a name is valid, so Python
>> could allow
>> this too:
>>     <expression>.<keyword>
>> Keyword arguments are also generally unambiguous, as they have to appear
>> within the
>> parens of an invocation, before the equals sign:
>>     <expression>(<keyword>=<expression>)
>> If Python allowed those three examples (but still prevented users from
>> *defining* names
>> that are keywords) new keywords could be introduced without breaking old
>> code , and the
>> language would only require relatively minor tweaking.
>> -- Carl Smith
>> carl.input at gmail.com
>> On 14 May 2018 at 19:11, Terry Reedy <tjreedy at udel.edu> wrote:
>>> On 5/14/2018 10:02 AM, Clint Hepner wrote:
>>>> On 2018 May 14 , at 6:47 a, Daniel Moisset <dmoisset at machinalis.com>
>>>>> wrote:
>>>>> Following up some of the discussions about the problems of adding
>>>>> keywords and Guido's proposal of making tokenization context-dependent, I
>>>>> wanted to propose an alternate way to go around the problem.
>>>> My main objection to what follows is that it doesn't seem to offer any
>>>> benefit over the current practice of appending an underscore (_) to a
>>>> keyword to make it a valid identifier.
>>> Tkinter uses this convention for a few option names that clash.
>>> --
>>> Terry Jan Reedy
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