[Python-Dev] A "record" type (was Re: Py2.6 ideas)

[Steven Bethard]

On 2/20/07, Larry Hastings <larry at hastings.org> wrote:
>      # the easy way to define a "subclass" of record
>      def Point(x, y):
>          return record(x = x, y = y)
>
>      # you can use hack-y features to make your "subclasses" more swell
>      def Point(x, y):
>          x = record(x = x, y = y)
>          # a hack to print the name "Point" instead of "record"
>          x.__classname__ = "Point"
>          # a hack to impose an ordering on the repr() display
>          x.__names__ = ("x", "y")
>          return x
>
>      p = Point(3, 5)
>      q = Point(2, y=5)
>      r = Point(y=2, x=4)
>      print p, q, r
>
>      # test pickling
>      import pickle
>      pikl = pickle.dumps(p)
>      pp = pickle.loads(pikl)
>      print pp
>      print pp == p
>
>      # test that the output repr works to construct
>      s = repr(p)
>      print repr(s)
>      peval = eval(s)
>      print peval
>      print p == peval
>  ------
>
>  Yeah, I considered using __slots__, but that was gonna take too long.

Here's a simple implementation using __slots__:

http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/502237

And you don't have to hack anything to get good help() and a nice
repr(). Declare a simple class for your type and you're ready to go::

    >>> class Point(Record):
    ...     __slots__ = 'x', 'y'
    ...
    >>> Point(3, 4)
    Point(x=3, y=4)

STeVe
-- 
I'm not *in*-sane. Indeed, I am so far *out* of sane that you appear a
tiny blip on the distant coast of sanity.
        --- Bucky Katt, Get Fuzzy