[Qgis-developer] New API: get attribute values from a PostGIS layer

[Vincent Mora]

Hi Stephan,

We modified the postgis-workshop tutorial for qgis plugin development to
use the new python api of qgis 1.9, there are examples of feature access
in there:

https://github.com/Oslandia/postgis-workshop

Cheers,

Vincent.

On 17/07/2013 21:13, Stéphane Henriod wrote:
> Dear all
>
> I am trying to get into the new 2.0 API and am still facing issues for
> very basic stuff: getting the values of the attributes out of a
> PostGIS layer.
>
> Basically, it works (with the almost same code) in the Qgis python
> console, but I don't manage to get it to work in a stand-alone script.
>
> What I have so far is a PostGIS layer, that I load with:
>
>     /uri = QgsDataSourceURI()
>     uri.setConnection('localhost', '5432', 'db_name', 'user_name',
>     'password')
>     uri.setDataSource('my_schema', 'my_table', 'the_geom')
>        
>     my_layer = QgsVectorLayer(uri.uri(),'myhospitals','postgres')
>     /
>
>
> A quick test shows me that the layer has been successfully loaded:
>
>     /if not my_layer.isValid():
>         print "Layer failed to load!"
>     else:
>         print "Layer loaded successfully"
>     /
>
>
> I would assume that
>
>     /for elem in my_layer.getFeatures():/
>     /    print elem.attributes()/
>
>
> should return the attributes in a usable format but, instead, I get:
> /
> /
>
>     /[<PyQt4.QtCore.QVariant object at 0xad37aca4>,
>     <PyQt4.QtCore.QVariant object at 0xad37acdc>, None,
>     <PyQt4.QtCore.QVariant object at 0xad37ad14>]/
>     /[<PyQt4.QtCore.QVariant object at 0xad37aca4>,
>     <PyQt4.QtCore.QVariant object at 0xad37acdc>,
>     <PyQt4.QtCore.QVariant object at 0xad37ad14>,
>     <PyQt4.QtCore.QVariant object at 0xad37ad4c>]/
>     /[<PyQt4.QtCore.QVariant object at 0xad37aca4>,
>     <PyQt4.QtCore.QVariant object at 0xad37acdc>,
>     <PyQt4.QtCore.QVariant object at 0xad37ad14>,
>     <PyQt4.QtCore.QVariant object at 0xad37ad4c>]/
>     /[<PyQt4.QtCore.QVariant object at 0xad37aca4>,
>     <PyQt4.QtCore.QVariant object at 0xad37acdc>,
>     <PyQt4.QtCore.QVariant object at 0xad37ad14>,
>     <PyQt4.QtCore.QVariant object at 0xad37ad4c>]/
>
>
> Does anyone have an idea where the problem could lie?
>
> For those who speak French, the question is posted here as well:
> http://www.forumsig.org/showthread.php/37178-Nouvelle-API-r%C3%A9cup%C3%A9rer-les-valeurs-attributaires
>
> I am using Qgis 1.9.0 with Python 2.7 on Ubuntu 13.04
>
> Thanks in advance for ideas and comments...
>
> Cheers
>
> Stéphane
> --
> "Le mot progrès n'aura aucun sens tant qu'il y aura des enfants
> malheureux" -- Albert Einstein
>
> "A journey does not need reasons. Before long, it proves to be reason
> enough in itself. One thinks that one is going to make a journey, yet
> soon it is the journey that makes or unmakes you." -- Nicolas Bouvier
>
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>
>
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