using datetime containers

indika indikabandara19 at gmail.com
Sun Nov 9 06:56:43 CET 2008



indika wrote:
> Marc 'BlackJack' Rintsch wrote:
> > On Sat, 08 Nov 2008 08:07:15 -0800, indika wrote:
> >
> > > John Machin wrote:
> > >> On Nov 8, 6:06�pm, indika <indikabandar... at gmail.com> wrote:
> > >> > Or else, I would have expected the datatime.date object has a
> > >> > writeable data member, so that iterating a calender with
> > >> > itermonthdates would allow me to access that data member.
> > >>
> > >> Sorry, I can't begin to guess what you mean by that.
> > >
> > > I was referring to something like this
> > >
> > > eg. in an Image processing lib
> > >
> > > struct Image
> > > {
> > > char* p_Data; // image data
> > > int i_DataLen; // length of data
> > > void* p_UserData; // user attaches whatever }
> > > If the lib user attaches some struct related to image name, file
> > > location ... to p_UserData
> > > whenever a Image* is passed around the user has access to those.
> > >
> > > Similarly, if a datetime.date object had an attribute which the user can
> > > access he could
> > > d1 = datetime.date.(2008, 1, 1)
> > > d1.UserData = x1 // hypothetical
> > >
> > > d2 = datetime.date.(2008, 1, 2)
> > > d2.UserData = x2 // hypothetical
> > >
> > > mylist.append([d1, d2])
> > >
> > > Hope i'm making some sense :-)
> >
> > You can subclass `datetime.date` and attach whatever attributes you
> > want.  Be sure to overwrite `__new__()` because `datetime.date` objects
> > are immutable.
> >
> > Ciao,
> > 	Marc 'BlackJack' Rintsch
>
>
> Thanks.
>
> As I read somewhere python has almost everything you need. So I
> wouldn't go to subclassing existing stuff and making life harder for
> me.
>
> Eventhough it may be costly to sort after adding all items to the
> dict(as opposed to inserting with a custom sort function) I would go
> for that.
>
> Anyway, I saw the UserDict module which may help in creating a custom
> dictionary with a custom comparison function. (I didn't go to detail
> as the documentation was not very elaborate )

while trying out the sorting method i realized that u can *never*
insert the sorted data to dict !!!
>>> m1
{datetime.date(2008, 1, 1): 'b', datetime.date(2008, 1, 3): 'c',
datetime.date(2008, 1, 2): 'a'}

>>> l = sorted(m1.items(), cmp=cmpr) // cmpr is date comp function
>>> for i, j in l:
...     m3[i] = j;
...
>>> m3
{datetime.date(2008, 1, 1): 'b', datetime.date(2008, 1, 3): 'c',
datetime.date(2008, 1, 2): 'a'}

so then there's no point in sorting.
it will only be possible to do a linear search i.e. sort and add to
list then search from top.

I would really like to suggest some wrapper or an enhanced dict
structure which has a configurable comparison function that will be
used to insert and find keys.
this will help, for example, if we want to go to a specific key and
iterate from there onwards





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