Tricks to do "enums"?

[Gareth McCaughan]

Neil Schemenauer wrote:

> "==" works just as well.  Python smart enough to try a pointer
> compare first.  The code path is almost the same so I doubt there
> would be much speed gained by using "is".

Er, surely it will fall back on a string comparison if
the two aren't pointer-equal?

I think concern about efficiency is misplaced here,
in any case.

    >>> import time
    >>> x = range(500000)
    >>> y = map(str, x)
    >>> def test_i():
    ...   t0 = time.time()
    ...   u = map(lambda t: t==5000, x)
    ...   t1 = time.time()
    ...   return t1-t0
    ...
    >>> def test_s():
    ...   t0 = time.time()
    ...   u = map(lambda t: t=='5000', x)
    ...   t1 = time.time()
    ...   return t1-t0
    ...
    >>> test_i()
    1.45546197891
    >>> test_i()
    1.34740400314
    >>> test_s()
    1.71845293045
    >>> test_s()
    1.70223104954
    >>> 1.702/1.347
    1.26354862658

If the difference in speed is only 25% here, it's unlikely
to be a big deal in any real program. (I don't mean that the
cost of a string compare is only 25% more than that of an
integer compare; that's not the point.)

-- 
Gareth McCaughan  Gareth.McCaughan at pobox.com
sig under construction