Use set/dict literal syntax

[alok]

Every supported version can use this syntax, and it's both faster and clearer.

[codecov-io]

Codecov Report

Merging #169 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #169   +/-   ##
=======================================
  Coverage   83.85%   83.85%           
=======================================
  Files           1        1           
  Lines         539      539           
  Branches       95       95           
=======================================
  Hits          452      452           
  Misses         63       63           
  Partials       24       24

Impacted Files	Coverage Δ
cloudpickle/cloudpickle.py	83.85% <100%> (ø)	⬆️

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[HyukjinKwon]

to me, im okay with it

[HyukjinKwon]

indentation a bit weird here tho.

[alok]

Fixed.

[alok]

Fixed lint errors.

[HyukjinKwon]

@alok BTW, mind checking if cloudpickle roughly worked on Python 2.6 too? I know it's something we don't officially support; however, if that worked before and this change breaks it, I doubt if we should fix these only for style reason.

[llllllllll]

set literals were added in 2.7, so this will not work with 2.6. Though, if it is not supported, it is not supported, right?

[HyukjinKwon]

Correct but I was thinking I wouldn't bother to fix styles if that breaks a potential practical use case. There's no gain here rather than styles but we might lose a practical use case.

[HyukjinKwon]

dictionary and set comprehensions are good but set(...) and dict(...) are not deprecated and proper usage here too IIRC - if they are deprecated, it's fine.

If there's no gain better than styles, I would like to know if this was already broken with Python 2.6. It wouldn't be too challenging.

[alok]

@HyukjinKwon This syntax won't work in 2.6.

set() and dict() are not deprecated, but the way they're used in cloudpickle is not their intended use. They're meant for converting data structures other than comprehensions. Those are covered by the literal syntax.

I think it's worth ignoring 2.6 anyway. Python 2 end-of-life is in 1 year, 7 months, 30 days, 2 hours, and 25 minutes as of this moment. I've yet to see someone use 2.6 these days. Any version of python 2 below 2.7 is not supported by any major library, and the entire scientific python stack is pretty much on 3+ now.

Using this as a rough metric, about 0.2% of pypi downloads are for 2.6. That's not a large enough userbase for me to care about a version of python released a decade ago.

[HyukjinKwon]

Yup, I am aware of the history for Python 2.x and that syntax is specific to 2.7. Note that old OS already has 2.6 built-in Python and probably 2.6 wouldn't be newly installed on purpose much. In my previous company, there were thousands of customers relying on it. I personally think It needs another decade to ignore and push away Python 2.6.

I would be fine if there's better cases that could be fixed by something Python 2.7 has specifically but was less sure of these since there's a (unofficial) cost and risk we should take here.

For clarification, I am okay if anyone feels fine with it. I don't get in the way. It's -0 from me (Apache way).

[HyukjinKwon]

I have just merged. Thanks @alok and @llllllllll.