Use Python 3-styled sets in Python 2

Question

In Python 3, set-notation more closely matches the way sets are represented in set-theory while Python 2 uses a list style (i.e. set_py3 = {"A","B","C"} \ set_py2 = set(["A","B","C"]))

Is there any way to port the set-notation from Python 3 to Python 2 using from __future__?

Py2.7 let's one use the {"A","B","C"} set-notation but when it's printed, it is still set(["A","B","C"]) . I saw the from __future__ import braces but I don't think that introduces this type of set-notation. I know you can import the new print function with from __future__ import print_function. I wasn't sure if there was a similar method for porting set-notation.

Also do note that `{}` is an empty dictionary. `set()` is still the only way to do the empty set. — Antti Haapala -- Слава Україні, Nov 30 '15 at 17:28
You could maybe subclass Set and override __str__() or __repr__() to get the output side as you want it. — Reblochon Masque, Nov 30 '15 at 17:30
I usually use `dict()` for empty dictionaries. I was mainly thinking of the result being `{"A","B","C"}` when I print it instead of `set(["A","B","C"])` — O.rka, Nov 30 '15 at 17:34
No, there is no way to change the behavior of `set.__repr__` — Andrea Corbellini, Nov 30 '15 at 17:37
@AnttiHaapala, well to avoid writing `set` you can still write `{x for x in []}` :) — bgusach, Nov 30 '15 at 17:40
Note that `ipython` will pretty-print sets the way you want. [Related](http://stackoverflow.com/q/21110915/674039). — wim, Nov 30 '15 at 17:59

score -1 · Accepted Answer · edited Jun 20 '20 at 09:12

There were some features ported to Python 2.7 from 3.1, which include the set expression syntax; and other things:

Much as Python 2.6 incorporated features from Python 3.0, version 2.7 incorporates some of the new features in Python 3.1. The 2.x series continues to provide tools for migrating to the 3.x series.

A partial list of 3.1 features that were backported to 2.7:

The syntax for set literals ({1,2,3} is a mutable set).

Dictionary and set comprehensions ({i: i*2 for i in range(3)}).

Multiple context managers in a single with statement.

A new version of the io library, rewritten in C for performance.

The ordered-dictionary type described in PEP 372: Adding an Ordered Dictionary to collections.

The new "," format specifier described in PEP 378: Format Specifier for Thousands Separator.

The memoryview object.

...

So, to use the new syntax, simply upgrade to Python 2.7

–1 the user is asking about the repr of sets. they are not asking about the literal syntax for *creating* a set. — wim, Nov 30 '15 at 17:54

Use Python 3-styled sets in Python 2

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