21
votes
Accepted
Getting field names of layer using PyQGIS
To get field names with fields() method or other field properties (length, type, comment, ...) you can use:
field_names = [field.name() for field in layer.fields()]
# ['id', 'attr1', 'attr2', 'attr3']
...
- 64.3k
16
votes
Accepted
Running PyQGIS algorithm on selected features in layer
You need add the layer to project.
For add without showing it use:
QgsProject.instance().addMapLayer(layer1, False)
Example using only one layer:
layer1 = QgsVectorLayer(r"C:\test\grassland....
- 7,580
15
votes
Accepted
QGIS 3.0.2 Check if a field exists in a layer in Python
Welcome to GIS.SE!
As you thought, there is a way to know if a field exists in a layer not by iterating features but by looking at the layer structure.
In the QGIS Layers Panel, select a layer.
Then ...
- 34.9k
15
votes
Getting field names of layer using PyQGIS
List field names with dataProvider() method
from qgis.utils import iface
# get active layer if not already set
layer = iface.activeLayer()
prov = layer.dataProvider()
field_names = [field.name() ...
- 933
14
votes
Modify Attribute Table while opening using PyQGIS
Interesting question! I couldn't find any native signal emitted when an attribute table is opened or closed so I would call this solution a fairly inelegant workaround but it seems to work well enough....
- 18k
13
votes
Accepted
Modifying layer name in the layout legend with PyQGIS 3
You must set setUseLayerName() to False to name legend tree layers manually.
#
# previous lines
#
for i, layer in enumerate(layersToAdd):
tree_layer = root.addLayer(layer)
tree_layer....
- 64.3k
12
votes
Accepted
Getting layer by name using PyQGIS 3
If you are sure there is one layer named LAYER_NAME, the shortest way:
layer = QgsProject.instance().mapLayersByName('LAYER_NAME')[0]
In that way, you can get a layer in a group layer.
print(layer)
...
- 64.3k
12
votes
Accepted
Getting ordered list of IDs of selected features using PyQGIS
Use this script:
selection = []
def selection_changed(selected, deselected, clearAndSelect):
global selection
# If the user deselects feature(s), remove ID's from list
if deselected:
...
- 64.3k
12
votes
Accepted
Field calculator: generate n fields reporting n-largest values
You can use this script. First, select a the layer, then run the script. It adds the result as a memory layer. You should save the result as a new file manually or using a code.
input_layer = iface....
- 64.3k
12
votes
Accepted
Filtering with setSubsetString using PyQGIS
Change
layer.setSubsetString("GAMME_DE_S=VSR")
to
layer.setSubsetString("GAMME_DE_S='VSR'")
Then to add the layer,
if not layer.isValid():
print("Layer failed to load!&...
- 29.5k
11
votes
Accepted
Find QGIS 3 plugin folder location with PyQGIS
try:
from qgis.core import QgsApplication
QgsApplication.qgisSettingsDirPath()
for show profiles folder
https://qgis.org/api/classQgsApplication.html#a89ad50b0d0fd60ccae803f22f6c5cf46
- 7,580
11
votes
Creating vector layer in memory following the QGIS Python Programming Cookbook
If you are using QGIS 3 that book is outdated in hopes of improving your abilities around PyQGIS 3. Following code has 3 necessary corrections to run as expected:
layer = QgsVectorLayer('Point?crs=...
- 27.7k
11
votes
Accepted
Print Layout Items. setExtent() and attemptResize()
The order of when you set the extent, add the map to the layout, and resize the rectangle is important. Steps to add a map to a new layout in QGIS 3.
Instantiate the map object with QgsLayoutItemMap(...
- 535
11
votes
Accepted
Adding tile layer via PyQGIS
Here is the code which is working for me:
urlWithParams = 'type=xyz&url=https://a.tile.openstreetmap.org/%7Bz%7D/%7Bx%7D/%7By%7D.png&zmax=19&zmin=0&crs=EPSG3857'
rlayer = ...
- 892
11
votes
Accepted
Creating grid with PyQGIS
You use wrong TYPE code. You have to use 2 for rectangular grid. 3 means diamond.
params = {'TYPE':2, ...} # 2: rectangle
For more details about the algorithm try
import processing
processing....
- 64.3k
11
votes
Checking if active layer is GeoPackage using PyQGIS
You can use:
if iface.activeLayer().storageType() != 'GPKG':
print('Active layer is not a GeoPackage format')
- 1,260
10
votes
Accepted
Joining layers with PyQGIS 3
The class has been renamed from QgsVectorJoinInfo to QgsVectorLayerJoinInfo.
You now need to call each join function with their associated parameter:
...
csvField = 'id'
shpField = 'ID'
joinObject = ...
- 73.8k
10
votes
Accepted
Exporting layout in standalone script with QGIS 3
Here is the solution working for me. The python file must be in the same directory as the QGIS 3 project file :
#!/usr/bin/env python3
import os
from qgis.core import (QgsProject, QgsLayoutExporter, ...
- 14.5k
10
votes
Accepted
PyQGIS - Managing print layouts
You attempt to set a name to a deleted object.
You need to create a new object :
[...]
for layout in layouts_list:
if layout.name() == layoutName:
manager.removeLayout(layout)
layout = ...
- 14.5k
10
votes
Accepted
Apply a color ramp to vector layer using PyQGIS3
Updated answer:
Below is a recipe to apply a graduated renderer based on values in an attribute field, specifying the number of classes and color ramp.
# Set layer name and desired paremeters
...
- 18k
10
votes
Accepted
Zoom to feature by clicking cell in the Attribute Table
I've found a temporary solution:
layer = QgsProject.instance().mapLayersByName("LAYER_NAME")[0]
attr_table = iface.showAttributeTable(layer)
table = attr_table.findChildren(QTableView)[0]
def ...
- 64.3k
10
votes
Accepted
Get only fields with datatype int in PyQGIS
By type name (typeName()):
int_types = ["Integer", "Integer64"]
int_fields = [field for field in iface.activeLayer().fields() if field.typeName() in int_types]
OR by type number (...
- 64.3k
10
votes
Accepted
Adding page number to an atlas layout with PyQGIS 3
You can use the following structure:
#
# previous lines
#
page_label = QgsLayoutItemLabel(layout)
#
# other label settings here
#
text = "[% 'Page: ' + to_string(@atlas_featurenumber ) + '/' +...
- 64.3k
10
votes
Accepted
Populating attributes while creating polygons in for-loop from CSV using PyQGIS
You set feature fields to empty QgsFields.
fields = QgsFields() # fields is empty
feature.setFields(fields) # you set the empty fields
Instead, pass layer.fields() to QgsFeature.
feature = QgsFeature(...
- 64.3k
10
votes
Accepted
Iterating over features of a same layer
If you use != (in n.id()!=init.id()) inside the "if" statement, you compare the items (ex: comparing 2 to 1) you've compared before (ex: comparing 1 to 2). In this case, both items are ...
- 64.3k
10
votes
Accepted
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 ...
- 64.3k
9
votes
How can I get the path for an input layer in a QGIS 3 script?
The input parameters can be accessed as a dictionary object, so parameters['SPECIES_POINTS'] will give you the path to the input layer. The call to the algorithm would then be:
pointsReprojected = ...
- 5,194
9
votes
Accepted
Moving a geometry using PyQGIS3
To change QgsFeature geometry in QGIS 3 you have to call setGeometry() explicitly.
geom = feat.geometry()
geom.translate(100, 100)
feat.setGeometry(geom)
Explanation:
In QGIS 2 geometry() returns a ...
- 660
9
votes
Accepted
Applying categorized render to polygons
Improved answer
The trick is to use renderer.updateColorRamp(ramp) instead of renderer.setSourceColorRamp(ramp).
Here is a working code snippet to create categories from unique values, pass them to a ...
- 18k
9
votes
Accepted
Add Help Menu entry in QGIS 3 from `startup.py`
Great idea
you need place startup.py in C:\Users\<username>\AppData\Roaming\QGIS\QGIS3
and add missing import ,and voilá
from qgis.utils import iface
from PyQt5.QtWidgets import QAction
import ...
- 7,580
Only top scored, non community-wiki answers of a minimum length are eligible