[Qgis-developer] Use qgis libraries in python scripts

[Martin Dobias]

Hi Minja

On Fri, Jul 9, 2010 at 10:19 AM, Minja <msiljegovic at gmail.com> wrote:
> Im trying to create standalone python application that will use PyQT4
> libraries and QGIS libriaries. I installed first python 3.1 and tested it in
> console and Eclipse PyDev enviroment. It worked fine....then I installed
> PyQt GPL v4.7.3 for Python 3.1, tested import of those libraries and
> everything worked fine on both console and eclipse enviroment.
>
> My next step was to try to use qgis libraries and I followed tutorial from
> this site http://mapserver.sk/~wonder/qgis/html/intro.html to configure
> enviroment variables for using PyQGIS in my standalone application. But when
> I test "from qgis.core import *" Im getting error message  "from qgis.core
> import *  ImportError: DLL load failed: The specified procedure could not be
> found" all the time.

Python binding shipped with QGIS (both OSGeo4W and standalone) are
compiled against Python 2.x releases, so don't expect that it will
work with Python 3. Please use Python 2 and I _strongly_ recommend you
to use Python from OSGeo4W installation to prevent further troubles.

You _may_ have some success with Python 3 if you compiled QGIS with
bindings from source code, though the procedure might require some
tweaking and so far I am not aware of any effort in order to compile
and run QGIS with Python 3. At some point of time in future, QGIS will
use Python 3 by default, but nowadays everyone still uses Python 2.x.



> Here is how mine enviroment variables are set
> PYTHONPATH:
> C:\Python31\Lib\site-packages;C:\OSGeo4W\apps\qgis-unstable\python;
> PATH: C:\OSGeo4W\apps\qgis-unstable;C:\Python31\Lib\site-packages\PyQt4\bin;
> I also tried with options to set following paths in
> PATH C:\OSGeo4W\apps\qgis-unstable\bin;C:\OSGeo4W\apps\qgis-unstable\lib;
> I read a lot about this on internet and forums, I also saw comments that I
> should use python and PyQt installation that comes with QGIS(version 1.4.0)(
> I tried that running OSGeo4W shell and it worked), but I think it would be
> better to dont be dependent directly to OSGeo installation...I would like
> only to use QGIS librarires same as it is happenning with PyQT4.

I don't understand why you try to be independent from the OSGeo4W
installation. Having all the libraries in place (and working well) is
a huge advantage of OSGeo4W. If you do that to ensure that you don't
have to carry the whole OSGeo4W installation with your custom
application, then don't worry. You can simply copy only necessary
components (Python, SIP, PyQt4, QGIS and its dependencies) from it,
just like you would do it otherwise anyway.

Regards
Martin