[gdal-dev] How to wrap a C++ library using GDAL in a Python library?

[Brendan Ward]

Alex,

see rasterio: https://github.com/mapbox/rasterio

It uses Cython (https://cython.readthedocs.io/en/latest/index.html) to wrap
GDAL rasters and related functions for use in Python.  You can use Cython
to wrap C / C++ libraries for use in Python; how much you wrap depends on
the interface you want between the two.

Hope that helps,

Brendan

On Tue, Dec 8, 2020 at 10:17 AM Alex HighViz <alexhighviz at hotmail.com>
wrote:

> Hi Paul,
>
> Yes there is a generic, "how do I expose a  C++ library to Python users"
> question. But there is a GDAL specific issue that the main inputs and
> outputs in my library are raster layers, and I am not sure how to pass
> those. Especially if my library is using GDAL and the user is using GDAL
> through Python. I can make my interface completely based on filenames, but
> that seems inefficient. Is this not a more commonly encountered problem?
>
> Thanks, Alex
>
> Get Outlook for Android <https://aka.ms/ghei36>
>
> ------------------------------
> *From:* Paul Harwood <runette at gmail.com>
> *Sent:* Tuesday, December 8, 2020 4:46:07 PM
> *To:* Alex HighViz <alexhighviz at hotmail.com>
> *Cc:* gdal-dev at lists.osgeo.org <gdal-dev at lists.osgeo.org>
> *Subject:* Re: [gdal-dev] How to wrap a C++ library using GDAL in a
> Python library?
>
> I may have misunderstood but I think you are asking the wrong community.
>
> You can take your own C++ library and make it available to a Python
> library - see https://docs.python.org/3/extending/extending.html etc -
> but this is not the community to ask for advice about that. You can, of
> course, access GDAL in that c++ library using the c++ API but I don't think
> that doing so would change how you expose the API from your library in
> Python ...
>
> Perhaps you need to make your question more specific?
>
> On Tue, 8 Dec 2020 at 12:37, Alex HighViz <alexhighviz at hotmail.com> wrote:
>
> Hello,
>
> Could somebody please put me on the right track with the following
> problem?
>
> I have a C++ library that makes use of GDAL for processing raster maps and
> I would like to wrap some of its features into a Python library to make it
> accessible to a wider community.
>
> I would like my library to present functions that take rasters as input
> and produce rasters as outputs.  I can modify the C++ side to have the
> functions work on GDALRasterBands, GDALDatasets, or just on filenames. From
> my perspective I'd prefer to write any wrapping / boiler plate in C++ and
> have the Python parts as small as possible.
>
> I know this question has been asked before here, but I don't recall the
> answer and could not find it again. A simple example of "best practice"
> would be ideal.
>
>
> With many thanks, Alex
>
>
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-- 
Brendan C. Ward
Owner | Lead Software Engineer
Astute Spruce, LLC
astutespruce.com
541-250-9544
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