9
votes
Accepted
Use PyQGIS to save memory layer to GeoPackage that does not already exist
You can use the following lines in your PyQGIS script to make an empty GeoPackage.
from osgeo import ogr
gpkg_path = "c:/test/test.gpkg"
ds = ogr.GetDriverByName('GPKG').CreateDataSource(...
- 76.1k
8
votes
Accepted
Adding simple Geomasking (Donut masking) feature using PyQGIS
Preamble: Unfortunatelly I did not read your articles, but I hope I understood your issue correctly.
Let's assume there is an input point layer called 'points2', see the image below.
The task is the ...
- 31.3k
7
votes
Accepted
Where is the source code for the Processing Plugin "Buffer"?
The buffer algorithm is implemented in C++: https://github.com/qgis/QGIS/blob/fbc2082b7e25042c5f82cb000c52d84625b31624/src/analysis/processing/qgsalgorithmbuffer.cpp
The Buffer.py file you found is ...
- 10.7k
7
votes
Accepted
Saving and applying layout of columns in QGIS Attribute Table
I can suggest a PyQGIS approach to (1) adjust, (2) export, (3) downgrade and (4) finally import configurations applied to the attribute table of a layer. It is mainly based on the ...
- 31.3k
7
votes
Saving and applying layout of columns in QGIS Attribute Table
You export the layer as a layer definition file and then just add this file to QGIS to load the layer.
For more control and in-place replacement, you can export the table component of the layer style.
...
- 40.7k
7
votes
Determining on which side of line points are located using QGIS
In PyQGIS 3 there is a handy method available, namely segmentSide() from the QgsGeometryUtils class.
Let's assume there are two layers: a line layer with a single feature, and a point layer with nine ...
- 31.3k
7
votes
Accepted
Adding custom panel to QGIS
Your question is quite broad but here is a short example to get you started. It will make a QgsFileWidget (a native widget for selecting directories/files) and place it in a dock widget on the right ...
- 14.7k
6
votes
Determining on which side of line points are located using QGIS
You can also use QGIS expressions for this, using this expression to get a 0 or 1 output for each point, depending on which side of the line it is (see below for curved lines). The solution is based ...
- 67.2k
6
votes
Use PyQGIS to save memory layer to GeoPackage that does not already exist
Just to round out the list of alternatives, the first script can be made to work for a new file by changing the option for gdal:convertformat (wrapper for ogr2ogr) from -update to -overwrite - ...
- 3,705
6
votes
Accepted
Editing width of drop down field list in the QGIS Attribute Table
There is a PyQGIS solution I can suggest. Honestly, it was tricky, and not straightforward.
The thing you are looking for is the QFrame hidden under AttributeTable / mUpdateExpressionBox / mFieldCombo....
- 31.3k
5
votes
Accepted
What is QDomNode and QDomDocument in terms of PyQGIS?
Here is what QDomNode and QDomDocument are in the Qt context:
The QDomDocumentclass represents the entire XML document. Conceptually, it is the root of the document tree, and provides the primary ...
- 76.1k
5
votes
Use PyQGIS to save memory layer to GeoPackage that does not already exist
The second script works if you change the flag to the correct one which is QgsVectorFileWriter.CreateOrOverwriteFile:
# reference to memory layer
layer = iface.activeLayer()
# save location
...
- 3,342
4
votes
Changing Widget type to 'Unique Values' and making it editable using PyQGIS
Try this:
layer = iface.activeLayer()
# start with a list of your fields to edit
mt20_fields = ['POINT_ADDR', 'STEET_ROAD', 'LANDMARK']
# fields must be iterated through:
for field in mt20_fields:
...
- 137
4
votes
Accepted
Calling Turf.js nearest point function equivalent in QGIS using a Python script
You can use the QgsSpatialIndex class which has a nearestNeighbor() method.
E.g. to iterate over a point layer, finding the nearest point and distance for each feature, you could do something like:
...
- 20.6k
4
votes
Problem to interface a script with python in QGIS
Add import processing to import section to get rid of NameError.
Since you use self.parameterAsSource, you get NoneType object .. error. Instead, use self.parameterAsRasterLayer.
Use the script below....
- 76.1k
4
votes
What is QDomNode and QDomDocument in terms of PyQGIS?
After certain trials and errors, I was able to perform exporting/importing configurations of the layer's attribute table, see Saving and applying layout of columns in QGIS Attribute Table.
Despite a ...
- 31.3k
4
votes
Editing width of drop down field list in the QGIS Attribute Table
To complement @Taras's answer with a simpler python code (changed with edit):
# imports
from qgis.utils import iface
from qgis.core import QgsProject
from PyQt5.QtWidgets import QApplication, QFrame
#...
- 3,342
3
votes
Accepted
Interpolating polygon values based on neighbouring polygons in QGIS
You dont specify how you want to interpolate.
This buffers the grey polygons and use the surrounding polygons values to calculate the average, with the intersection areas as weights.
So a polygon with ...
- 68.8k
3
votes
Accepted
QGIS Action to "enable" (display) a raster layer that is already loaded
You can use the following code in your Python action script.
from qgis.utils import iface
project = QgsProject.instance()
layer_id = '[%@layer_id%]'
fid = [%$id%]
layer_obj = QgsProject().instance()....
- 20.6k
3
votes
_core.QgsProcessingException: Unable to execute algorithm Incorrect parameter value for TARGET_LAYER
I solved my own issue passing target_layer as an URI layer doing:
# Define the connection parameters using QgsDataSourceUri
uri = QgsDataSourceUri()
uri.setConnection(host, port, dbname, user, ...
- 51
3
votes
Accepted
"Incorrect parameter value for LAYERS" error when saving CSV to GeoPackage with PyQGIS
You can make a QgsVectorLayer of your CSV URI which will be accepted by the package algorithm.
A couple of things to note:
The %dir suffix is missing from your CSV URI in the LAYERS property of the ...
- 14.7k
3
votes
Accepted
Using label placement via PyQGIS
The QgsVectorLayer class has no method like placement. However, the QgsPalLayerSettings does.
I suppose you are trying to apply this LabelPlacement mode.
Just add this settings.placement = Qgis....
- 31.3k
3
votes
Accepted
Refresh one layer style
Probably the call you are missing is layer.triggerRepaint()
Try:
style_path = r'Path\to\style_file.qml'
lyr = iface.activeLayer()
lyr.loadNamedStyle(style_path)
lyr.triggerRepaint()
# update ...
- 20.6k
3
votes
Loading multiband raster layer with pseudocolor style (not RGB) using PyQGIS
This is a pretty good tutorial on how to do what you want.
edit: this is also how the pyqgis documentation says it should be done documentation
raster_file_path = "path/to/raster.ext"
...
- 3,342
2
votes
Prevent custom Processing Algorithm from returning output on error
You could use https://qgis.org/pyqgis/3.28/core/QgsProcessingException.html :
from qgis.core import QgsProcessingException
[...]
raise QgsProcessingException("Your message here")
- 1,935
2
votes
Accepted
Setting path for QgsLayoutItemPicture using PyQGIS
You can use QgsLayoutItemPicture.setMode() (see here for available formats):
project = QgsProject.instance()
manager = project.layoutManager()
layout = QgsPrintLayout(project)
layout....
- 14.7k
1
vote
Setting dropdown on feature attribute form using plugin
You can set the value map on an existing field like so:
fields = layer.fields()
idx = fields.indexFromName(field_name)
field_values = ['Dewasa', 'Kanak-kanak']
# use dictionary comprehension to make ...
- 14.7k
1
vote
Accepted
Run processing tools in Python console
In the params you have the output 'output', which is just a string. But you need to use the variable output
Then replace processing.run(algo, params) with the following:
processing.runAndLoadResults(...
- 652
1
vote
Loading multiband raster layer with pseudocolor style (not RGB) using PyQGIS
I found a solution to switch the renderer to a QgsSingleBandPseudoColorRenderer in a single line with default values by using the class widget QgsSingleBandPseudoColorRendererWidget:
raster_layer = ...
- 3,342
1
vote
Understanding the QGIS API documentation based on the featureCount() method with legendKey parameter
I use QGIS 3.28 so I don't have the legendKeys() method available. I've used legendSymbolItems() instead. And it turned out I don't need countSymbolFeatures() anyway. QGIS API docs cheated me.
As I ...
- 148
Only top scored, non community-wiki answers of a minimum length are eligible