19
votes
Accepted
Explaining long computing time of Python code
Here are some issues with your script:
I've already learned that using GeoJSON for analyzing is a too bad idea. The script below that takes 20 seconds when I use GeoPackage takes about 8-10 hours ...
- 76.1k
12
votes
Accepted
Calling "Remove empty layers" plugin from the Python Console in QGIS
Yes. It is possible using the following lines.
from RemoveEmptyLayers.removeemptylayers import RemoveEmptyLayers
remove = RemoveEmptyLayers(iface)
remove.run()
Please also check this answer to ...
- 76.1k
12
votes
Accepted
Append several layers to a GeoJSON file with PyQGIS
You need to tell the code what to do when it encounters the same file. For this, you need to use for the second export:
options = QgsVectorFileWriter.SaveVectorOptions()
options.actionOnExistingFile = ...
- 76.1k
12
votes
Accepted
Creating one meter line from a point in the direction of a other line using PyQGIS
Change the for loop as follows:
for point_feat in point_layer.getFeatures():
point_geom = point_feat.geometry()
nearest_ids = line_index.nearestNeighbor(point_geom.asPoint(), 1)
...
- 76.1k
12
votes
Accepted
"'QgsPyExpressionFunction' object is not callable" when using custom function within QgsPyExpressionFunctions in PyQGIS
The problem is not about feature or parent parameter. It arises because the string in QgsExpression is not a valid QGIS expression.
attrmap_filtered.values() in the expression is a Pythonic syntax, ...
- 76.1k
12
votes
Rotating features with multiple geometries in one layer using PyQGIS
There are several things that I would improve:
do not forget to start/startEditing, end/endEditCommand(), and commit/commitChanges() editings
use the setGeometry() method properly, otherwise the ...
- 31.3k
11
votes
Accepted
Deleting parts of MultiPolygon based on area using PyQGIS
You can make a new part list from the MultiPolygon instead of deleting the parts.
layer = iface.activeLayer()
# Minimum area threshold
minimum_area = 2000
layer.startEditing()
# Loop through all ...
- 76.1k
11
votes
Install Python library in QGIS as non-administrator
Since you don't have admin privileges, when you install a package using QGIS Python Console/Editor as follows, it is installed to C:\Users\user\AppData\Roaming folder.
import subprocess
subprocess....
- 76.1k
11
votes
Accepted
Closing QGIS project without saving using PyQGIS
As @etrimaille stated, "editing a layer" and "saving the project" are two different things, and you can edit data (and saving) without saving the project itself.
A project is not a ...
- 76.1k
11
votes
Accepted
Translating raster from floating point to int16 increases size
Your 5 Mb inputs are compressed and your outputs are not.
Your 40 Mb inputs may be compressed, but didn't compress well (very noisy data leads to poor compression, a random raster can actually ...
- 64.8k
10
votes
Creating spatial index in standalone script as part of output vector layer using PyQGIS
If you use layer_out.dataProvider().createSpatialIndex() you don't get that error. To get the error you must use layer_out.createSpatialIndex(). The code in the question doesn't throw the error: ...
- 76.1k
10
votes
PyQGIS to set masked symbol layer and mask source
Label masking information is not stored in the qml-file?
I guess "Masked symbol layers" and "Mask sources" settings are not stored in both qml file and Geopackage. I just realized ...
- 76.1k
10
votes
Accepted
Performing basic labelling with PyQGIS
There is no problem with @Kezah's answer. I've edited the script and it works. Please check it. Avoid using startEditing() and dataProvider().addFeatures() together. Use either one. If you construct a ...
- 76.1k
10
votes
Accepted
Why angleAtVertex() returns different value than angle_at_vertex in Field Calculator using PyQGIS
angle_at_vertex() returns the angle in degrees:
anlge_at_vertex($geometry, 0) -> 38.618825502347555 degree
angleAtVertex() returns the angle in radians:
feature.geometry().angleAtVertex(0) -> 0....
- 76.1k
10
votes
Accepted
Get name of labeling rule with Python in QGIS
You have to use description method of class QgsRuleBasedLabeling.Rule.
layer = iface.activeLayer()
labeling = layer.labeling()
for rule in labeling.rootRule().children():
print(rule.description())...
- 76.1k
10
votes
Accepted
Running Python code easily for end users in QGIS
You can use the minimal plugin skeleton in this repository. Copy the files (only metadata and __init__ are required) to a new folder in plugin folder. Change the files' content as follows:
Folder ...
- 76.1k
10
votes
Accepted
Set the Units of a QgsGeometryGeneratorSymbolLayer object in PyQGIS
You have to use QgsUnitTypes.RenderMillimeters.
layer = iface.activeLayer()
mm = QgsUnitTypes.RenderMillimeters
layer.renderer().symbol().symbolLayer(1).setUnits(mm)
symbolLayer(1) must be an ...
- 76.1k
10
votes
Accepted
Use PyQGIS to load Value Map against attribute
To set a value map widget with values loaded manually, you can just do something like:
#QgsVectorLayer object
vl = iface.activeLayer()
# Get field index
fld_idx = vl.fields().lookupField('...
- 20.6k
10
votes
Accepted
Hiding/showing layers in legend does not work in QGIS standalone
QgsLayerTreeMapCanvasBridge must be in global scope. But you define bridge in add_legend method's scope. Therefore, variable bridge is gone after add_legend finished.
One of the solutions:
Add bridge ...
- 76.1k
9
votes
Accepted
QGIS Python loop integer with select by expression
You can use the following script structure:
layer = iface.activeLayer()
end_number = 5 # OS1, OS2, OS3, OS4, OS5
attribute_name = "attribute_name" # field name containing OS values
for i ...
- 76.1k
9
votes
Making dissolve output as temporary layer using PyQGIS
In more recent versions of QGIS, do not forget to include the 'SEPARATE_DISJOINT' argument, see the Changelog for QGIS 3.26 for more details.
So, your code may look like this:
from qgis import ...
- 31.3k
9
votes
Accepted
Accessing processing.run() output layer in PyQGIS
Regarding the question: "do I need to use is_child_algorithm=True?", you need to use it if the algorithm you are running is being run as a child or sub-algorithm, if you like, inside the ...
- 20.6k
9
votes
Accepted
Zooming to each vector layer extent, one at a time, using PyQGIS
You can solve your issue using QTimer which controls when to execute functions and it's asynchronous, i.e., it allows other functions to continue to run (think of a map.refresh()) while waiting some ...
- 76.1k
9
votes
"AttributeError: 'dict' object has no attribute 'fields'" error when creating and deleting fields in the attribute table using PyQGIS
I could get the same error:
Traceback (most recent call last):
File "C:\PROGRA~1\QGIS32~1.0\apps\Python39\lib\code.py", line 90, in runcode
exec(code, self.locals)
File "<...
- 31.3k
9
votes
PyQt signal when layer name is changed in PyQGIS
Use the nameChanged signal of QgsLayerTreeNode class.
from qgis.core import QgsProject
def name_changed(node, name):
print(f"New Name: {name}")
QgsProject.instance().layerTreeRoot()...
- 76.1k
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
What does context mean in PyQGIS?
I would like to explain as far as I know what context means.
Context can be seen as a bucket to pass information around.(Ref)
Let's say you write a function (funcA) which calls another function (...
- 1,421
8
votes
Accepted
PyQGIS: setting layer styles with QML file from URL
Instead of loadNamedStyle use the method importNamedStyle. It can directly receive a XML document as argument instead of a file path.
Creating an XML document is simply using QDomDocument::setContent()...
- 3,306
8
votes
Accepted
"Could not load source layer for MASK: invalid value" error when iterating over features in polygon layer and clipping raster by mask layer in PyQGIS
Apparently, the type of Mask layer should be a [vector: polygon] i.e. QgsVectorLayer, see documentation.
Also, visible via processing.algorithmHelp("gdal:cliprasterbymasklayer"):
...
MASK: ...
- 31.3k
8
votes
Accepted
TypeError when converting shapefiles to KMLs using PyQGIS
According to the documentation the first argument should be a QgsVectorLayer, which is why you are getting the unexpected type error.
You are also missing the QgsCoordinateReferenceSystem parameter.
...
- 14.7k
Only top scored, non community-wiki answers of a minimum length are eligible