[Python-ideas] Empty set, Empty dict

[Clint Hepner]

There's one more, even more obvious (IMO) option for an empty set literal: U+2205, EMPTY SET. But that opens a whole other can of worms, namely expanding the grammar to allow Unicode characters outside of identifiers.

> On Jun 22, 2014, at 5:25 AM, "Philipp A." <flying-sheep at web.de> wrote:
> 
> of course it’s ugly, but it’s also obvious that it had to be suggested, because it’s the only obvious idea.
> 
> which leaves us with either a non-obvious idea or no empty set literal, which is a bit sad and inconsistent.
> 
> if i’d develop a language from scratch, i’d possibly use the following empty literals:
> 
> [] = list; () = tuple, {} = set
> [:] = ordered dict, (:) = named tuple, {:} = dict
> 
> but that ship has sailed.
> 
> 
> 2014-06-10 18:39 GMT+02:00 Guido van Rossum <guido at python.org>:
>> No. Jeez. :-(
>> 
>> 
>>> On Tue, Jun 10, 2014 at 9:25 AM, Ryan Gonzalez <rymg19 at gmail.com> wrote:
>>> +1 for using {,}.
>>> 
>>> 
>>>> On Tue, Jun 10, 2014 at 4:07 AM, Wichert Akkerman <wichert at wiggy.net> wrote:
>>>> Victor Stinner wrote:
>>>> 2014-06-10 8:15 GMT+02:00 Neil Girdhar <mistersheik at gmail.com>:
>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> > I've seen this proposed before, and I personally would love this, but my
>>>>> > guess is that it breaks too much code for too little gain.
>>>>> >
>>>>> > On Wednesday, May 21, 2014 12:33:30 PM UTC-4, Frédéric Legembre wrote:
>>>>> >>
>>>>> >>
>>>>> >>    Now   |  Future  |
>>>>> >> ----------------------------------------------------
>>>>> >>    ()    |   ()     |  empty tuple  ( 1, 2, 3 )
>>>>> >>    []    |   []     |  empty list   [ 1, 2, 3 ]
>>>>> >>    set() |   {}     |  empty set    { 1, 2, 3 }
>>>>> >>    {}    |   {:}    |  empty dict   { 1:a, 2:b, 3:c }
>>>>> 
>>>>> 
>>>>> Your guess is right. It will break all Python 2 and Python 3 in the world.
>>>>> 
>>>>> Technically, set((1, 2)) is different than {1, 2}: the first creates a
>>>>> tuple and loads the global name "set" (which can be replaced at
>>>>> runtime!), whereas the later uses bytecode and only store values
>>>>> (numbers 1 and 2).
>>>>> 
>>>>> It would be nice to have a syntax for empty set, but {} is a no-no.
>>>> 
>>>> Perhaps {,} would be a possible spelling. For consistency you might want to allow (,) to create an empty tuple as well; personally I would find that more intuitive that (()).
>>>> Wichert.
>>>>  
>>>> 
>>>> 
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>>> 
>>> 
>>> 
>>> -- 
>>> Ryan
>>> If anybody ever asks me why I prefer C++ to C, my answer will be simple: "It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was nul-terminated."
>>> 
>>> 
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>> 
>> 
>> 
>> -- 
>> --Guido van Rossum (python.org/~guido)
>> 
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