[Qgis-user] Problem loading several provider libs from external script
Gary Sherman
gsherman at geoapt.com
Mon Feb 25 15:15:09 PST 2013
Try setting QGIS_PREFIX_PATH=/usr
Then make sure the path to the QGIS libs is either configured in
ld.so.conf.d/ or LD_LIBRARY_PATH
In my case, I have QGIS installed in /home/gsherman/qgis_master and this
sequence works:
>From the shell:
export LD_LIBRARY_PATH=/home/gsherman/qgis_master/lib
export QGIS_PREFIX_PATH=/home/gsherman/qgis_master
export PYTHONPATH=/home/gsherman/qgis_master/share/qgis/python
In Python:
app = QgsApplication(['/home/gsherman/qgis_master'], False)
app.initQgis()
for provider in QgsProviderRegistry.instance().providerList():
print provider
...:
WFS
delimitedtext
gdal
gpx
memory
mssql
ogr
osm
ows
postgres
spatialite
sqlanywhere
wcs
wms
On Mon, Feb 25, 2013 at 12:45 AM, Nils Olaf de Reus
<nils.de.reus at gmail.com>wrote:
> Hi everyone,
>
> When trying to use the qgis libraries from an external script (that
> is, a script running not within the context of the embedded console of
> QGIS), I get only a severely limited selection of available data
> providers. A number of libraries that load fine from inside the
> context of QGIS' embedded python console, fail to load when initQgis
> is used from a standalone external script.
>
> I have a Linux 2.6.32-5-amd64 x86_64 GNU/Linux platform, running
> Debian Squeeze and the 1.8 release of QGIS for Squeeze from the
> official repository at http://qgis.org/debian. To test if the problem
> described below still existed with a newer version of QGIS, I created
> a clean Debian Squeeze chroot environment, and installed the latest
> nightly build. The problem still existed with the nightly, same as in
> the 1.8 release.
>
>
> The provider lib files are present in the usual plugin directory:
>
> nils at fennek:~$ ls /usr/lib/qgis/plugins
> libcoordinatecaptureplugin.so libmemoryprovider.so
> libdelimitedtextplugin.so libmssqlprovider.so
> libdelimitedtextprovider.so libofflineeditingplugin.so
> libdiagramoverlay.so libogrprovider.so
> libdxf2shpconverterplugin.so liboracleplugin.so
> libevis.so libosmprovider.so
> libgdalprovider.so libpostgresprovider.so
> libgeorefplugin.so librasterterrainplugin.so
> libgpsimporterplugin.so libroadgraphplugin.so
> libgpxprovider.so libspatialiteprovider.so
> libgrassplugin.so libspatialqueryplugin.so
> libgrassprovider.so libspitplugin.so
> libgrassrasterprovider.so libwfsprovider.so
> libheatmapplugin.so libwmsprovider.so
> libinterpolationplugin.so libzonalstatisticsplugin.so
>
>
> My external script goes through the usual steps, shown below in an
> interactive session for easy replication:
>
> nils at fennek:~$ python
> Python 2.6.6 (r266:84292, Dec 26 2010, 22:31:48)
> [GCC 4.4.5] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
> >>> from qgis.core import *
> >>> app = QgsApplication([u'/usr'], False)
> >>> print app.showSettings()
> Application state:
> Prefix: /usr
> Plugin Path: /usr/lib/qgis/plugins
> Package Data Path: /usr/share/qgis
> Active Theme Name:
> Active Theme Path: :/images/themes//
> Default Theme Path: :/images/themes/default/
> SVG Search Paths: /usr/share/qgis/svg/
> /home/nils/.qgis//svg/
> User DB Path: /usr/share/qgis/resources/qgis.db
>
> >>> app.initQgis()
>
> Now if I check which providers are there, I only get three..
>
> >>> for provider in QgsProviderRegistry.instance().providerList():
> ... print provider
> ...
> delimitedtext
> gdal
> gpx
>
>
> ..while that exact same statement inside Qgis' embedded Python Console
> yields all thirteen providers:
>
> >>> for provider in QgsProviderRegistry.instance().providerList():
> ... print provider
> ...
> WFS
> delimitedtext
> gdal
> gpx
> grass
> grassraster
> memory
> mssql
> ogr
> osm
> postgres
> spatialite
> wms
>
>
> Sofar, I've traced it to the point where during initQgis(), the
> creation of the QgsProviderRegistry will reject those libraries that
> return False on the test if QLibrary's load() method will succesfully
> load them. This too can be shown from the interactive python console.
> First in the external console:
>
> >>> from PyQt4 import QtCore
> >>>
> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libdelimitedtextprovider.so').load()
> True
> >>> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libgdalprovider.so').load()
> True
> >>> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libgpxprovider.so').load()
> True
> >>> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libogrprovider.so').load()
> False
> >>>
> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libspatialiteprovider.so').load()
> False
> >>>
>
> ..well, I think you see the pattern. Outside of those three
> ('delimitedtext', 'gpx' and 'gdal'), QLibrary doesn't seem able to
> load any of the other provider libraries.
>
> Now my first guess when QLibrary can't load a library would be that
> something is wrong with that library. Except of course that when these
> same commands are issued inside the embedded console under Qgis, these
> same libs load fine:
>
> >>> from PyQt4 import QtCore
> >>>
> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libdelimitedtextprovider.so').load()
> True
> >>> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libgdalprovider.so').load()
> True
> >>> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libgpxprovider.so').load()
> True
> >>> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libogrprovider.so').load()
> True
> >>>
> QtCore.QLibrary(u'/usr/lib/qgis/plugins/libspatialiteprovider.so').load()
> True
> >>>
>
>
> I've tried making my sys.path identical between the embedded and
> external python sessions. No effect.
>
> I didn't see any obvious systematic problems with the libraries that
> didn't load (I focussed on libmemoryprovider, because that one is
> relatively simple), and neither in the ldd nor readelf outputs did
> anything stand out as an obvious red flag. (I say 'obvious red flag'
> because I lack the expertise to properly understand even half the
> things that come out of readelf, and can only look for a limited
> number of 'telltale signs')
>
> So.. what am I missing? Is there some other library that Qgis preloads
> that makes the loading of the other dynamically linked providers work?
> And how can I get that to also happen from a regular python script not
> inside the embedded python console?
>
>
> Kind regards,
> Nils
> _______________________________________________
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> Qgis-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user
>
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