[Qgis-user] Pyqgis how to append existing gpkg layer

[andrea antonello]

Hi German,


> that's right Andrea. It actually depends on whether you want to append
> features to an existing layer, or to "append" (one could also say "create")
> a layer (in)to an existing GPKG database. The latter case is well covered
> by Anne's answer.
>
> See prior messages in this thread:
> https://lists.osgeo.org/pipermail/qgis-user/2023-April/052855.html
>

ah, sorry, I missed that part somehow.
Thanks, cheers,
Andrea



>
> Regards,
>
> Germán
>
>
> El mié, 26 abr 2023 a las 9:11, andrea antonello via QGIS-User (<
> qgis-user at lists.osgeo.org>) escribió:
>
>> Hi, from what I saw in the docs, you should be able to append to layers
>> with the filewriter option AppendToLayerNoNewFields?
>> The CreateOrOverwriteLayer overwrites the layer completely.
>>
>> Cheers,
>> Andrea
>>
>>
>> On Wed, Apr 26, 2023 at 2:58 PM Anne B. Nilsen via QGIS-User <
>> qgis-user at lists.osgeo.org> wrote:
>>
>>> I’m not a pyQGIS-expert, but with help from gis.stackechange.com I have
>>> managed to create an empty geopackage file and then adding several layers
>>> to it with this code:
>>>
>>> …
>>>
>>> gpkg_reg = "karplanteregistrering.gpkg"                   # the NEW gpkg
>>> to be created
>>>
>>> if os.path.exists(gpkg_reg):                              # If gpkg-file
>>> already exists, delete it
>>>
>>>     os.remove(gpkg_reg)
>>>
>>> …
>>>
>>> #
>>> https://gis.stackexchange.com/questions/417916/creating-empty-layers-in-a-geopackage-using-pyqgis?noredirect=1&lq=1
>>>
>>> def create_blank_gpkg_layer(gpkg_path: str, layer_name: str, geometry:
>>> int,
>>>
>>>                             crs: str, fields: QgsFields, append: bool =
>>> False
>>>
>>>                             ) -> bool:
>>>
>>>     # To add a layer to an existing GPKG file, pass 'append' as True
>>>
>>>     options = QgsVectorFileWriter.SaveVectorOptions()
>>>
>>>     options.driverName = "GPKG"
>>>
>>>     options.layerName = layer_name
>>>
>>>     if append:
>>>
>>>         options.actionOnExistingFile =
>>> QgsVectorFileWriter.CreateOrOverwriteLayer
>>>
>>>         writer = QgsVectorFileWriter.create(
>>>
>>>         gpkg_path,
>>>
>>>         fields,
>>>
>>>         geometry,
>>>
>>>         QgsCoordinateReferenceSystem(crs),
>>>
>>>         QgsCoordinateTransformContext(),
>>>
>>>         options)
>>>
>>>     del writer
>>>
>>>     return True
>>>
>>> …
>>>
>>> # Layer 1 oversikt – creating an empty layer with attributes read from a
>>> csv-file
>>>
>>> f = open("./egenskaper/egenskaper_oversikt.csv",'r') # open file
>>>
>>> f.readline()  # read the first line of the file (the "metadata"/heading)
>>>
>>> layer_name = "oversikt"              # set layer name
>>>
>>> print('creates layer', layer_name)   # print layer name
>>>
>>> geom = QgsWkbTypes.PointZ            # geometrytype
>>>
>>> crs = 'epsg:25832'                   # coordinate system
>>>
>>> fields = QgsFields()
>>>
>>> for line in f:                       # Read attrubutes from csv-file
>>>
>>>      r = {}
>>>
>>>      r = line.split(';')  # 0 navn, 1 QVariant-type, 2 lengde og 3
>>> presisjon
>>>
>>>      fname = r[0]
>>>
>>>      l = int(r[2])
>>>
>>>      p = int(r[3])
>>>
>>>      try:
>>>
>>>           fields.append(QgsField(fname,set_variant(r[1]),'',l,p))  # add
>>> field to layer
>>>
>>>      except:
>>>
>>>           print("Noe gikk galt - får ikke laget egenskaper fra " +str(f))
>>>
>>> f.close()  # close file
>>>
>>> create_blank_gpkg_layer(gpkg_reg, layer_name, geom, crs, fields)  # Do
>>> NOT include True when the FIRST layer is created
>>>
>>>
>>>
>>> # Layer 2 arter (to be added to the same new gpkg-file just created
>>> above)
>>>
>>> f = open("./egenskaper/egenskaper_arter.csv",'r') # open file
>>>
>>> f.readline()
>>>
>>> layer_name = "arter"
>>>
>>> print('creates layer', layer_name)   # print layer name
>>>
>>> geom = QgsWkbTypes.PointZ            # geometrytype
>>>
>>> crs = 'epsg:25832'                   # coordinate system
>>>
>>> fields = QgsFields()
>>>
>>> for line in f:                       # Read attrubutes from csv-file
>>>
>>>      r = {}
>>>
>>>      r = line.split(';')  # 0 navn, 1 QVariant-type, 2 lengde og 3
>>> presisjon
>>>
>>>      fname = r[0]
>>>
>>>      l = int(r[2])
>>>
>>>      p = int(r[3])
>>>
>>>      try:
>>>
>>>           fields.append(QgsField(fname,set_variant(r[1]),'',l,p))  # add
>>> field to layer
>>>
>>>      except:
>>>
>>>           print("Noe gikk galt - får ikke laget egenskaper fra " +str(f))
>>>
>>> f.close()  # close file
>>>
>>> create_blank_gpkg_layer(gpkg_reg, layer_name, geom, crs, fields, True)
>>> # Include True to add a new layer to the SAME gpkg-file
>>>
>>> …
>>>
>>>
>>>
>>> Note the difference in the use of True and not when calling
>>> create_blank_gpk_layer().
>>>
>>> Perhaps something similar may be the solution to your problem.
>>>
>>>
>>>
>>> Kind regards
>>>
>>> Anne
>>>
>>>
>>>
>>>
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>
>
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