Re: [Python-Dev] Sets, Dictionaries

[Eric Fahlgren]

On Thu, Mar 29, 2018 at 10:11 AM, David Mertz  wrote:

> I agree with everything Steven says. But it's true that even as a 20-year
> Python user, this is an error I make moderately often when I want an empty
> set... Notwithstanding that I typed it thousands of times before sets even
> existed (and still type it when I want an empty dictionary).
>
> That said, I've sort of got in the habit of using the type initializers:
>
> x = set()
> y = dict()
> z = list()
>
> I feel like those jump out a little better visually. But I'm inconsistent
> in my code.
>

​
Yeah, we've been doing that for several years, too.  A hair slower in some
cases, but much more greppable...

​
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Re: [Python-Dev] Sets, Dictionaries

[David Mertz]

I agree with everything Steven says. But it's true that even as a 20-year
Python user, this is an error I make moderately often when I want an empty
set... Notwithstanding that I typed it thousands of times before sets even
existed (and still type it when I want an empty dictionary).

That said, I've sort of got in the habit of using the type initializers:

x = set()
y = dict()
z = list()

I feel like those jump out a little better visually. But I'm inconsistent
in my code.

On Thu, Mar 29, 2018, 2:03 AM Steven D'Aprano  wrote:

> Hi Julia, and welcome!
>
> On Wed, Mar 28, 2018 at 09:14:53PM -0700, Julia Kim wrote:
>
> > My suggestion is to change the syntax for creating an empty set and an
> > empty dictionary as following.
> >
> > an_empty_set = {}
> > an_empty_dictionary = {:}
> >
> > It would seem to make more sense.
>
> Indeed it would, and if sets had existed in Python since the beginning,
> that's probably exactly what we would have done. But unfortunately they
> didn't, and {} has meant an empty dict forever.
>
> The requirement to keep backwards-compatibility is a very, very hard
> barrier to cross. I think we all acknowledge that it is sad and a little
> bit confusing that {} means a dict not a set, but it isn't sad or
> confusing enough to justify breaking millions of existing scripts and
> applications.
>
> Not to mention the confusing transition period when the community would
> be using *both* standards at the same time, which could easily last ten
> years.
>
> Given that, I think we just have to accept that having to use set() for
> the empty set instead of {} is a minor wart on the language that we're
> stuck with.
>
> If you disagree, and think that you have a concrete plan that can make
> this transition work, we'll be happy to hear it, but you'll almost
> certainly need to write a PEP before it could be accepted.
>
> https://www.python.org/dev/peps/
>
>
> Thanks,
>
> --
> Steve
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Re: [Python-Dev] Sets, Dictionaries

[Stephen Hansen]

On Wed, Mar 28, 2018, at 9:14 PM, Julia Kim wrote:
> My suggestion is to change the syntax for creating an empty set and an 
> empty dictionary as following.
> 
> an_empty_set = {}
> an_empty_dictionary = {:}
> 
> It would seem to make more sense.

The amount of code this would break is astronomical. 

-- 
Stephen Hansen
  m e @ i x o k a i  . i o
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Re: [Python-Dev] Sets, Dictionaries

[Steven D'Aprano]

Hi Julia, and welcome!

On Wed, Mar 28, 2018 at 09:14:53PM -0700, Julia Kim wrote:

> My suggestion is to change the syntax for creating an empty set and an 
> empty dictionary as following.
> 
> an_empty_set = {}
> an_empty_dictionary = {:}
> 
> It would seem to make more sense.

Indeed it would, and if sets had existed in Python since the beginning, 
that's probably exactly what we would have done. But unfortunately they 
didn't, and {} has meant an empty dict forever.

The requirement to keep backwards-compatibility is a very, very hard 
barrier to cross. I think we all acknowledge that it is sad and a little 
bit confusing that {} means a dict not a set, but it isn't sad or 
confusing enough to justify breaking millions of existing scripts and 
applications.

Not to mention the confusing transition period when the community would 
be using *both* standards at the same time, which could easily last ten 
years.

Given that, I think we just have to accept that having to use set() for 
the empty set instead of {} is a minor wart on the language that we're 
stuck with.

If you disagree, and think that you have a concrete plan that can make 
this transition work, we'll be happy to hear it, but you'll almost 
certainly need to write a PEP before it could be accepted.

https://www.python.org/dev/peps/


Thanks,

-- 
Steve
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Re: [Python-Dev] Sets, Dictionaries

[Hasan Diwan]

Hi, Julia,

On 28 March 2018 at 21:14, Julia Kim  wrote:
>
> My suggestion is to change the syntax for creating an empty set and an
> empty dictionary as following.
>

You should craft your suggestion as a PEP and send it to the python-ideas
mailing list. Good luck! -- H

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[Python-Dev] Sets, Dictionaries

[Julia Kim]

Hi,

My name is Julia Hiyeon Kim.

My suggestion is to change the syntax for creating an empty set and an empty 
dictionary as following.

an_empty_set = {}
an_empty_dictionary = {:}

It would seem to make more sense.


Warm regards,
Julia Kim
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