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In QGIS 3.4 I can run algorithms under the General setting "Invalid features filtering" -> "Ignore features with invalid geometries" However, when I try Processing through Python functions like the qgis:fieldcalculator it just breaks. Is there a way to make my QGIS python interpreter recognize that I do not care for invalid geometries?

Here is an example of a working code with valid geometries which breaks when invalid :

import os
import sys
import gdal
gdal.UseExceptions()

from qgis.core import QgsApplication
from qgis.analysis import QgsNativeAlgorithms

QgsApplication.setPrefixPath(os.path.join("C:", os.sep, "OSGeo4W64", "apps", "qgis"), True)
qgs = QgsApplication([], False)
qgs.initQgis()

sys.path.append(os.path.join("C:", os.sep, "OSGeo4W64", "apps", "qgis", "python", "plugins"))
import processing
from processing.core.Processing import Processing

Processing.initialize()
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms())


def add_area(input_vector):
    out = "pathtooutput.shp"
    params = {
                'INPUT': input_vector,
                'FIELD_NAME': 'area',
                'FIELD_TYPE': 0,
                'FIELD_LENGTH': 10,
                'FIELD_PRECISION': 3,
                'NEW_FIELD': True,
                'FORMULA': ' $area ',
                'OUTPUT': out
                }
    res = processing.run("qgis:fieldcalculator", params)
    print(res)
    return out

inp = "path_to_testvector_with_invalid_or_valid_geometries_for_test.shp"

add_area(inp)
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8
  • 3
    Can you post an example of the code you've tried?
    – ndawson
    Commented Jan 2, 2019 at 17:14
  • It is not necessary, I try the same at QGIS with the "Invalid features filtering" -> "Ignore features with invalid geometries" and it works. I try "Invalid features filtering" -> "Stop algorithm execution when a geometry is invalid" and it finds invalid geometries, thus it stops.I know I have invalid geometries, so Python breaks QGIS Processing when it finds them, while when removed through side ways, it outputs properly.
    – ODstuck
    Commented Jan 2, 2019 at 21:08
  • The question is not a matter of code, but if in this python framework of QGIS there is an option that could be set somewhere
    – ODstuck
    Commented Jan 2, 2019 at 21:10
  • 1
    There is, but we'd need to see your current code to post the solution.
    – ndawson
    Commented Jan 2, 2019 at 23:10
  • There you go, hope it helps a solution and anyone trying python with qgis
    – ODstuck
    Commented Jan 3, 2019 at 15:13

1 Answer 1

Reset to default
15

Try changing the part:

params = {
            'INPUT': input_vector,
            'FIELD_NAME': 'area',
            'FIELD_TYPE': 0,
            'FIELD_LENGTH': 10,
            'FIELD_PRECISION': 3,
            'NEW_FIELD': True,
            'FORMULA': ' $area ',
            'OUTPUT': out
            }
res = processing.run("qgis:fieldcalculator", params)

to

params = {
            'INPUT': input_vector,
            'FIELD_NAME': 'area',
            'FIELD_TYPE': 0,
            'FIELD_LENGTH': 10,
            'FIELD_PRECISION': 3,
            'NEW_FIELD': True,
            'FORMULA': ' $area ',
            'OUTPUT': out
            }
context = dataobjects.createContext()
context.setInvalidGeometryCheck(QgsFeatureRequest.GeometryNoCheck)
res = processing.run("qgis:fieldcalculator", params, context=context)

You'll also need to add these imports:

from processing.tools import dataobjects
from qgis.core import QgsFeatureRequest
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3
  • 4
    It also needs the addition of "from qgis.core import QgsFeatureRequest", for the completeness of the answer
    – ODstuck
    Commented Feb 1, 2019 at 18:28
  • 1
    Apart from that, it works like a charm. Even adds the area. Attention to "context" param in processing call. Thanks a lot @ndawson
    – ODstuck
    Commented Feb 1, 2019 at 21:55
  • I have a similar problem to above, where I encounter this error: GEOS exception: TopologyException: Input geom 1 is invalid: Ring Self-intersection at or near point 1528924.0830000006 485361.14200000092 0 at 1528924.0830000006 485361.14200000092 0 Is there a different .setInvalidGeometryCheck option that would; help me here? I've tried the above but the native:intersection still fails.
    – grego
    Commented Dec 22, 2020 at 1:56

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