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[Python-Dev] Alternate notation for global variable assignments

Zack Weinberg zack at codesourcery.com
Mon Oct 27 17:55:04 EST 2003 
"Steve Holden" <sholden at holdenweb.com> writes:

>>
>>    :var       = value   # var in module scope
>>    :scope:var = value   # var in named enclosing scope
>>
>> An advantage of this notation is that it can be used anywhere, not
>> just in an assignment.  This has primary value for people reading the
>> code -- if you have a fairly large class method that uses a module
>> variable (not by assigning it) somewhere in the middle, writing it
>> :var means the reader knows to go look for the assignment way up top.
>> This should obviously be optional, to preserve backward compatibility.
>>
> However, its use in such expressions as
>
> 	sublist = lst[:var]
>
> would lead to substantial ambiguities, right?

I suppose it would.  Unfortunately, there's no other punctuation mark
that can really be used for the purpose -- I think both $ and @
(suggested elsewhere in response to a similar proposal) have
too many countervailing connotations.  Witness e.g. the suggestion
last week that $ become magic in string % dict notation.

Py-in-the-sky suggestion: make the slice separator character be ;
instead of :.  (Half serious.)

Somewhat warty suggestion: take lst[:var] to be a slice, but
lst[(:var)] to be a global variable reference.  And lst[:(:var)] to be
a slice on a global, etc. etc.

Better ideas solicited.

zw
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