15
votes
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']
...
- 55.5k
13
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....
- 13.6k
13
votes
Accepted
Getting field names of layer using PyQGIS
List field names with dataProvider() method
# get active layer if not already set
layer = qgis.utils.iface.activeLayer()
prov = layer.dataProvider()
field_names = [field.name() for field in prov....
- 869
12
votes
Accepted
Change vector layer symbology PyQGIS 3?
The easiest for me would be to check the properties of the symbology layer which contains symbol properties affecting the whole layer:
dir(symbol)
>>>['DynamicRotation', 'Fill', 'Hybrid', '...
- 72.2k
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:
...
- 55.5k
11
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 ...
- 33.6k
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If you are using QGIS 3 that book is outdated in hopes of improving your abilities around PyQGIS 3.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=...
- 25.9k
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
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....
- 55.5k
11
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....
- 55.5k
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')
- 1,198
10
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
- 7,186
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 = ...
- 72.2k
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
...
- 13.6k
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 (...
- 55.5k
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 ) + '/' +...
- 55.5k
10
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....
- 55.5k
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(...
- 55.5k
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 = ...
- 5,114
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 ...
- 13.6k
9
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 = ...
- 800
9
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!&...
- 28.6k
9
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 ...
- 55.5k
8
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 ...
- 620
8
votes
Accepted
Applying graduated renderer to polygon using PyQGIS 3?
I'm going to answer my own question in two ways.
First, I'll use the example from the PyQGIS Developer Cookbook. I initially struggled with this example but eventually got it working, so here is a ...
- 1,621
8
votes
Accepted
Dissolving using PyQGIS?
The easiest approach is to run the algorithm through the GUI, and then look in the Processing "history". You'll see the equivalent Python command shown there for the operation you just performed via ...
- 26.2k
8
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 ...
- 7,186
8
votes
Field calculator: generate n fields reporting n-largest values
You can also use the following script without any Processing tool. The script doesn't create any layer, it adds fields to the active layer and assigns values.
from PyQt5.QtCore import QVariant
lyr = ...
- 3,479
8
votes
Accepted
How to set field attribute of selected features to NULL with PyQGIS 3
NULL is defined in qgis.core
from qgis.core import NULL
with edit(layer):
for feature in layer.selectedFeatures():
feature.setAttribute('distance', NULL)
layer.updateFeature(...
- 26.2k
8
votes
Populating attributes while creating polygons in for-loop from CSV using PyQGIS
Personally, I prefer to use the changeAttributeValues() method of QgsVectorDataProvider (see API docs here) as I find it more reliable. This method takes an attributes map which is basically a ...
- 13.6k
Only top scored, non community-wiki answers of a minimum length are eligible