[Python-Dev] Set data type

[Ka-Ping Yee]

On Thu, 3 Feb 2000, Ka-Ping Yee wrote:
> On Thu, 3 Feb 2000, Greg Stein wrote:
> > 
> > I think the follow is just as readable, if not more so:
> > 
> >     >>> s = set(1, 5, 7)
> > 
> > Where set() is a new builtin, taking an arbitrary number of arguments and
> > returning a new Set type.

Oh, waitasec.  On further thought, this produces surprising
behaviour when compared to list() and tuple():

    >>> list((1, 2, 3))
    [1, 2, 3]
    >>> list(1, 2, 3)
    Traceback (innermost last):
      File "<stdin>", line 1, in ?
    TypeError: list() argument must be a sequence
    >>> list(3)
    Traceback (innermost last):
      File "<stdin>", line 1, in ?
    TypeError: list() argument must be a sequence
    >>> tuple([1, 2, 3])
    (1, 2, 3)
    >>> tuple(3)
    Traceback (innermost last):
      File "<stdin>", line 1, in ?
    TypeError: tuple() argument must be a sequence

Now look...

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

    >>> set(1)
    # {1} or TypeError?

I still think set(x, y) -> {x, y} is nice, but it is unfortunate
that set() and list() would work differently.  Perhaps if we
think of set() in the same category as slice() it makes more sense.


-- ?!ng