[pdal] filter on return value

[Howard Butler]

> On Jun 3, 2015, at 3:28 PM, Luca Delucchi <lucadeluge at gmail.com> wrote:
> 
> - is there any documentations about the use of Python in/with PDAL?

The tests at https://github.com/PDAL/PDAL/tree/master/test/data/plang are probably the most documentation that exist at this point, unfortunately

> - could I use someway pdb inside the python function

PDB should Just Work if you are running from `pdal pipeline` in a terminal

> - how can I know the keys used by “ins"

There’s “ins” and “outs” dicts that contain numpy arrays that correspond to the data in the PointView at the time the predicate/programmable filter’s filter() method is invoked. Simply print (ins.keys()) to have it list what is available. Alternatively, if you are running with a pipeline or something, you can do `pdal info --schema thefile.las` to see what keys might be available to add to your filter.

> - could I pass some parameters to the function (I saw other functions
> and the usually use only ins and outs)

Can you describe what you might want to do here in more detail?

Howard