How can I use __setitem__ method of dict object?

[jeremito]

On Feb 7, 12:48 pm, Jussi Salmela <tiedon_j... at hotmail.com> wrote:
> jeremito kirjoitti:
>
> > On Feb 7, 8:28 am, "jeremito" <jerem... at gmail.com> wrote:
> >> On Feb 6, 5:10 pm, Bruno Desthuilliers
>
> >> <bdesth.quelquech... at free.quelquepart.fr> wrote:
> >>> jeremito a écrit :
> >>>  > On Feb 6, 2:36 pm, Bruno Desthuilliers > <bdesth.quelquech... at free.quelquepart.fr> wrote:
> >>> (snip)
> >>>  >>Here's an alternative implementation, so you get the idea.
> >>>  >>class Xs(dict):
> >>> oops ! I meant:
> >>>   class Xs(object):
> >>> of course...
> >>> (snip)
> >>>> I guess I just
> >>>> need more experience.
> >>> Possibly - but not only. You may want to have a look at the
> >>> FineManual(tm) for all this kind of "magic", starting with :http://docs.python.org/ref/specialnames.htmlhttp://docs.python.org/re...
> >>> HTH
> >> Thanks again!  Sometimes the problem is simply not knowing where to
> >> find the documentation, or finding the right portion of the
> >> documentation.  Your help has been invaluable.
>
> >> Jeremy
>
> > One more question.  I will be asking for the value of cs.xT *many*
> > (~millions) times.  Therefore I don't want it's value to be calculated
> > on the fly.  How can I set the value of xT whenever xS, xF, or xG are
> > changed, but not allow it to be set directly?  From the example given
> > previously, it seems like it can't be done this way.
>
> > Thans,
> > Jeremy
>
> I'm certainly no wizard in timing, but here goes:
>
> Using the class definition given to you by Bruno, adding the following
> to the end (and 'import timeit' at the start):
>
> #============
> lst = timeit.Timer('for i in xrange(10): xx=xs.xT', \
>                 'from __main__ import Xs;xs = Xs()').repeat(100,1000)
> lst.sort()
> print lst
> print 'Average:', sum(lst)/100
> #============
>
> I get the output:
> [0.017246605364648282, 0.01727426251101738, 0.017275659336591698,
> 0.017290745052793044, 0.01733264982001903, 0.017347735536220377,
>
>   and so on ...
>
> 0.029063749722380933, 0.029163762433493667, 0.029422733894950315,
> 0.029790378386079785]
> Average: 0.0182474979362
>
> Thus: A 1000 assignments take a little over 18 milliseconds. The largest
> values in the list are probably caused bu GC occurring. But even 30 ms /
> 1000 iterations i.e. 30 microseconds per fetch seems to be fast enough.
>
> All this depends of course on the computer used. Mine is on the fast
> side, you might test it on your PC.
>
> The correct way of programming is to find a good simple algorithm and
> the data structures needed, to program a clean solution with them and
> then when you've got a correctly operating application and THEN IF you
> need speed try to do something about it.
>
> "Premature optimization is the worst evil" or something like that is how
> the saying goes.
>
> Hopefully I'm not leading you astray by being a novice in using the
> timeit module.
>
> HTH,
> Jussi

Thank you.  Once again this mailing list has proven most helpful.  I
realize it probably isn't worth my time (or stress) to figure out how
to avoid calculating xT on the fly-at least not yet.

Jeremy