What do you think about Python's new Set Literal (2.7a3+)?

Question

What do you think about Python's new Set Literal (2.7a3+)?

>>> {1,1,2,3,3}
set([1, 2, 3])

Wouldn't it make some confusions with Array, If you came from different programming backgrounds like C/C++, C#, Java?

Answer 1

I guess it will take some getting used to.

Remember though that math uses that notation for sets.

I think set comprehensions are going to be quite nice though

It's a pity that they didn't make nested sets work with that notation

>>> {1,2,{3,4,5}}
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'set'

Perhaps f{} could make frozen sets the same say we use r'' for raw strings, then at least I could write

>>> {1,2,f{3,4,5}}

Answer 2

It makes sense, after all a set and a dictionary are related (I used to use a dictionary to emulate a set).

Answer 3

I'm not sure how often you need a set literal; if you're going to be listing the members literally, why not just avoid repeating them, and use a plain old list?

I also think it's weirdly inconsistent that you use {} to denote the set literal, but when printing itself, it uses []:

>>> {1,2,3,4,5}
set([1, 2, 3, 4, 5])

To me, it would make more sense if it repeated the actual literal syntax, i.e:

>>> {1,2,3,4,5}
{1, 2, 3, 4, 5}

or perhaps

>>> {1,2,3,4,5}
set({1, 2, 3, 4, 5})

Answer 4

Whatever your ground you find for it or against it, I feel "confusion with other language's features" is not a good justification.

It would also be consistent with all the collection literals you already have in Python.

• List: [1, 2, 3]
• Dictionary: {"one":1, "two":2, "three":3}
• Tuple: (1, 2, 3)
• And why not set? {1, 1, 2, 3}

My bottom line is that improving intra-language consistency wins over avoiding inter-language confusion

Answer 5

If anything, confusion within the language should be taken into account. Now you have to remember that {} specifies an empty dictionary, not a set.