Re: [PythonReports-users] SQLAlchemy optional relationships - what is recommended way to handle

[alexander s. <al...@go...>]

On 05.12.2012 22:24, Werner F. Bruhin wrote:
>
> Now to my question I define my fields like this:
>
> "drinkinfo.subregion_lv.name" and my "data" contains a few entries of
> type "cellarbook" each of them has "drinkinfo" relation and it I have
> things like "country_lv", "subregion_lv" etc etc, some of them are
> optional, i.e. not present on all rows.  How should that be defined in
> the "expr"?

There are at least two ways, depending on your goal:

1. Add "printwhen" condition to the style of your field.

2. Use conditional expression, something like 
"drinkinfo.subregion_lv.name if 'lv' in drinkinfo.subregions else '--'"

> Could I call a method of my own, something along these lines:
>
> def getRelInfo(objval, sainst):
>       """Get related information
>
>       :param objval: e.g. "drinkinfo.someoptionalrel.name"
>       :param sainst: an SA Instance of the row, e.g. a "cellarbook" entry/row
>       :return: the column value or blank
>
>       """

That is not a method, that's function.  To call a (non-builtin) function 
you have to import module defining that function.  See 
http://pythonreports.sourceforge.net/prt.shtml#import

And yes, you should be able to call any method of a data object.  Please 
see SQLAlchemy documentation if you need custom method on ORM objects.

Best wishes,
alex.