[CentralOH] Data Members / Properties - 2 questions

[Nick Albright]

Hey Mark!

I think you can use getattr() and setattr() instead of __dict__ and it'll
catch the property.

I hope that helps! (And I hope my memory is right ;)
 -Nick

On Sat, Feb 13, 2010 at 9:54 PM, Mark Erbaugh <mark at microenh.com> wrote:

> Hello all,
>
> I'm reworking some older code, changing it from using a cobbled together
> database based on shelves to use SQLITE3.
>
> I have several data objects stored as data members of a container object.
> These data members were read from the shelve when the container was created
> and saved when a save() method of the container was called. When the program
> needed the data is just accessed the member:  value = object.SHOW_QTY or
> object.SHOW_QTY = value
>
> Now the data lives in the SQLITE database. I would like to read and write
> the data from the database on demand.  It seems like a perfect place for a
> property.  For the above example, instead of SHOW_QTY being a data member it
> would be a property, thus the client code could still use value =
> object.SHOW_QTY and object.SHOW_QTY = value.
>
> The problem I have is that in some places, the existing code accesses these
> data members indirectly passing a string version of the data name (i.e.
> 'SHOW_QTY').  With a data member, it's a simple matter to look up the data
> in the container's __dict__.  However, it doesn't look like properties work
> the same way. At one time I had a semi understanding of how descriptors
> worked under the hood, but I've been away from this level of Python for a
> while...
>
> If you have an easy answer - great! If not, can you point me to a good
> reference to refresh my understanding?
>
> The answer to this question may also help with the second.  In creating
> these properties, I ended up with a lot of repetitive getters and setters.
>  The only difference was a parameter indicating which data element to use:
>
>     def _*getSHOW_QTY*(*self*):
>         return *self*._getAUDIT(*'SHOW_QTY'*)
>
>
>     def _*setSHOW_QTY*(*self*, data):
>         *self*._setAUDIT(*'SHOW_QTY'*, data)
>
>
>     def _*getBY_PILL*(*self*):
>         return *self*._getAUDIT(*'BY_PILL'*)
>
>
>     def _*setBY_PILL*(*self*, data):
>         *self*._setAUDIT(*'BY_PILL'*, data)
>
>
>     SHOW_QTY = property(_getSHOW_QTY, _setSHOW_QTY)
>     BY_PILL = property(_getBY_PILL, _setBY_PILL)
>
>
> There are several more properties like this. Is there a way to iterate
> through a sequence (i.e. (SHOW_QTY, BY_PILL, ...)) and have the getters,
> setters and properties created automatically?
>
> Thanks,
> Mark
>
>
>
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>
>


-- 
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