Cheat sheet for PyQgis
Change Look & Feel
from qgis.PyQt.QtWidgets import QApplication
app = QApplication.instance()
qss_file = open(r"/path/to/style/file.qss").read()
app.setStyleSheet(qss_file)
Change Icon and Title
from qgis.PyQt.QtGui import QIcon
icon = QIcon(r"/path/to/logo/file.png")
iface.mainWindow().setWindowIcon(icon)
iface.mainWindow().setWindowTitle("My QGIS")
Access Canvas
from qgis.utils import iface
canvas = iface.mapCanvas()
Change Canvas color
from qgis.PyQt.QtCore import Qt
iface.mapCanvas().setCanvasColor(Qt.black)
iface.mapCanvas().refresh()
CopyRight
from qgis.PyQt.Qt import QTextDocument
from qgis.PyQt.QtGui import QFont
mQFont = "Sans Serif"
mQFontsize = 9
mLabelQString = "© QGIS 2019"
mMarginHorizontal = 0
mMarginVertical = 0
mLabelQColor = "#FF0000"
INCHES_TO_MM = 0.0393700787402 # 1 millimeter = 0.0393700787402 inches
case = 2
def add_copyright(p, text, xOffset, yOffset):
p.translate( xOffset , yOffset )
text.drawContents(p)
p.setWorldTransform( p.worldTransform() )
def _on_render_complete(p):
deviceHeight = p.device().height() # Get paint device height on which this painter is currently painting
deviceWidth = p.device().width() # Get paint device width on which this painter is currently painting
# Create new container for structured rich text
text = QTextDocument()
font = QFont()
font.setFamily(mQFont)
font.setPointSize(int(mQFontsize))
text.setDefaultFont(font)
style = "<style type=\"text/css\"> p {color: " + mLabelQColor + "}</style>"
text.setHtml( style + "<p>" + mLabelQString + "</p>" )
# Text Size
size = text.size()
# RenderMillimeters
pixelsInchX = p.device().logicalDpiX()
pixelsInchY = p.device().logicalDpiY()
xOffset = pixelsInchX * INCHES_TO_MM * int(mMarginHorizontal)
yOffset = pixelsInchY * INCHES_TO_MM * int(mMarginVertical)
# Calculate positions
if case == 0:
# Top Left
add_copyright(p, text, xOffset, yOffset)
elif case == 1:
# Bottom Left
yOffset = deviceHeight - yOffset - size.height()
add_copyright(p, text, xOffset, yOffset)
elif case == 2:
# Top Right
xOffset = deviceWidth - xOffset - size.width()
add_copyright(p, text, xOffset, yOffset)
elif case == 3:
# Bottom Right
yOffset = deviceHeight - yOffset - size.height()
xOffset = deviceWidth - xOffset - size.width()
add_copyright(p, text, xOffset, yOffset)
elif case == 4:
# Top Center
xOffset = deviceWidth / 2
add_copyright(p, text, xOffset, yOffset)
else:
# Bottom Center
yOffset = deviceHeight - yOffset - size.height()
xOffset = deviceWidth / 2
add_copyright(p, text, xOffset, yOffset)
# Emitted when the canvas has rendered
iface.mapCanvas().renderComplete.connect(_on_render_complete)
# Repaint the canvas map
iface.mapCanvas().refresh()
Get algorithms list
from qgis.core import QgsApplication
for alg in QgsApplication.processingRegistry().algorithms():
print("{}:{} --> {}".format(alg.provider().name(), alg.name(), alg.displayName()))
# or
def alglist():
s = ''
for i in QgsApplication.processingRegistry().algorithms():
l = i.displayName().ljust(50, "-")
r = i.id()
s += '{}--->{}\n'.format(l, r)
print(s)
alglist()
Get algorithms Help
Random selection
import processing
processing.algorithmHelp("qgis:randomselection")
How many algorithms are there?
from qgis.core import QgsApplication
len(QgsApplication.processingRegistry().algorithms())
How many providers are there?
from qgis.core import QgsApplication
len(QgsApplication.processingRegistry().providers())
How many Expressions are there?
from qgis.core import QgsExpression
len(QgsExpression.Functions())
Access checked Layers
from qgis.utils import iface
iface.mapCanvas().layers()
Obtain Layers name
canvas = iface.mapCanvas()
layers = [canvas.layer(i) for i in range(canvas.layerCount())]
layers_names = [ layer.name() for layer in layers ]
print("layers TOC = ", layers_names)
# or
layers = [layer for layer in QgsProject.instance().mapLayers().values()]
Add vector layer
layer = iface.addVectorLayer("/path/to/shapefile/file.shp", "layer name you like", "ogr")
if not layer:
print("Layer failed to load!")
Find layer by name
from qgis.core import QgsProject
layer = QgsProject.instance().mapLayersByName("layer name you like")[0]
print(layer.name())
Set Active layer
from qgis.core import QgsProject
layer = QgsProject.instance().mapLayersByName("layer name you like")[0]
iface.setActiveLayer(layer)
Remove all layers
from qgis.core import QgsProject
QgsProject.instance().removeAllMapLayers()
Remove Contextual menu
ltv = iface.layerTreeView()
ltv.setMenuProvider( None )
See the CRS
from qgis.core import QgsProject
for layer in QgsProject().instance().mapLayers().values():
crs = layer.crs().authid()
layer.setName('{} ({})'.format(layer.name(), crs))
Set the CRS
from qgis.core import QgsProject, QgsCoordinateReferenceSystem
for layer in QgsProject().instance().mapLayers().values():
layer.setCrs(QgsCoordinateReferenceSystem(4326, QgsCoordinateReferenceSystem.EpsgCrsId))
Load all layers from GeoPackage
from qgis.core import QgsVectorLayer, QgsProject
fileName = "/path/to/gpkg/file.gpkg"
layer = QgsVectorLayer(fileName,"test","ogr")
subLayers =layer.dataProvider().subLayers()
for subLayer in subLayers:
name = subLayer.split('!!::!!')[1]
uri = "%s|layername=%s" % (fileName, name,)
# Create layer
sub_vlayer = QgsVectorLayer(uri, name, 'ogr')
# Add layer to map
QgsProject.instance().addMapLayer(sub_vlayer)
Load tile layer (XYZ-Layer)
from qgis.core import QgsRasterLayer, QgsProject
def loadXYZ(url, name):
rasterLyr = QgsRasterLayer("type=xyz&url=" + url, name, "wms")
QgsProject.instance().addMapLayer(rasterLyr)
urlWithParams = 'type=xyz&url=https://a.tile.openstreetmap.org/%7Bz%7D/%7Bx%7D/%7By%7D.png&zmax=19&zmin=0&crs=EPSG3857'
loadXYZ(urlWithParams, 'OpenStreetMap')
Load WCS layer
import urllib.parse
# Make WCS Uri
def makeWCSuri( url, layer ):
params = { 'dpiMode': 7 ,
'identifier': layer,
'url': url.split('?')[0] }
uri = urllib.parse.unquote( urllib.parse.urlencode(params) )
return uri
### Raster layer from WCS
rlayername = 'DEP3ElevationPrototype'
wcsUri = makeWCSuri('https://elevation.nationalmap.gov/arcgis/services/3DEPElevation/ImageServer/WCSServer', rlayername )
rlayer = QgsRasterLayer(wcsUri, 'DEP3ElevationPrototype', 'wcs')
if not rlayer.isValid():
print ("Layer failed to load!")
Root node
from qgis.core import QgsProject
root = QgsProject.instance().layerTreeRoot()
print (root)
print (root.children()
Access the first child node
from qgis.core import QgsLayerTreeGroup, QgsLayerTreeLayer
child0 = root.children()[0]
print (child0)
print (type(child0))
print (isinstance(child0, QgsLayerTreeLayer))
print (child0.parent())
Find groups and nodes
from qgis.core import QgsLayerTreeGroup, QgsLayerTreeLayer
for child in root.children():
if isinstance(child, QgsLayerTreeGroup):
print ("- group: " + child.name())
elif isinstance(child, QgsLayerTreeLayer):
print ("- layer: " + child.name() + " ID: " + child.layerId())
Find group by name
print (root.findGroup("Name"))
Add layer
from qgis.core import QgsVectorLayer, QgsProject
layer1 = QgsVectorLayer("Point?crs=EPSG:4326", "layer name you like", "memory")
QgsProject.instance().addMapLayer(layer1, False)
node_layer1 = root.addLayer(layer1)
Add Group
from qgis.core import QgsLayerTreeGroup
node_group2 = QgsLayerTreeGroup("Group 2")
root.addChildNode(node_group2)
Remove layer
root.removeLayer(layer1)
Remove group
root.removeChildNode(node_group2)
Move Node
cloned_group1 = node_group1.clone()
root.insertChildNode(0, cloned_group1)
root.removeChildNode(node_group1)
Rename None
node_group1.setName("Group X")
node_layer2.setName("Layer X")
Changing visibility
print (node_group1.isVisible())
node_group1.setItemVisibilityChecked(False)
node_layer2.setItemVisibilityChecked(False)
Expand Node
print (node_group1.isExpanded())
node_group1.setExpanded(False)
Hidden Node Trick
from qgis.core import QgsProject
model = iface.layerTreeView().layerTreeModel()
ltv = iface.layerTreeView()
root = QgsProject.instance().layerTreeRoot()
layer = QgsProject.instance().mapLayersByName('layer name you like')[0]
node=root.findLayer( layer.id())
index = model.node2index( node )
ltv.setRowHidden( index.row(), index.parent(), True )
node.setCustomProperty( 'nodeHidden', 'true')
ltv.setCurrentIndex(model.node2index(root))
Node Signals
def onWillAddChildren(node, indexFrom, indexTo):
print ("WILL ADD", node, indexFrom, indexTo)
def onAddedChildren(node, indexFrom, indexTo):
print ("ADDED", node, indexFrom, indexTo)
root.willAddChildren.connect(onWillAddChildren)
root.addedChildren.connect(onAddedChildren)
Create new TOC
from qgis.core import QgsProject, QgsLayerTreeModel
from qgis.gui import QgsLayerTreeView
root = QgsProject.instance().layerTreeRoot()
model = QgsLayerTreeModel(root)
view = QgsLayerTreeView()
view.setModel(model)
view.show()
Add Vector layer
from qgis.utils import iface
layer = iface.addVectorLayer("/path/to/shapefile/file.shp", "layer name you like", "ogr")
Get Active Layer
layer = iface.activeLayer()
List All Layers
from qgis.core import QgsProject
names = [layer.name() for layer in QgsProject.instance().mapLayers().values()]
Show methods
dir(layer)
Get Features
for f in layer.getFeatures():
print (f)
Get Selected Features
selectedFeatures = layer.selectedFeatureIds()
print(selectedFeatures)
Create a memory layer from selected features
memory_layer = layer.materialize(QgsFeatureRequest().setFilterFids(layer.selectedFeatureIds()))
QgsProject.instance().addMapLayer(memory_layer)
Get Geometry
for f in layer.getFeatures():
geom = f.geometry()
print ('%s, %s, %f, %f' % (f['NAME'], f['USE'],
geom.asPoint().y(), geom.asPoint().x()))
Hide a field column
from qgis.core import QgsEditorWidgetSetup
def fieldVisibility (layer,fname):
setup = QgsEditorWidgetSetup('Hidden', {})
for i, column in enumerate(layer.fields()):
if column.name()==fname:
layer.setEditorWidgetSetup(idx, setup)
break
else:
continue
Move geometry
geom = feat.geometry()
geom.translate(100, 100)
feat.setGeometry(geom)
Adding new feature
from qgis.core import QgsFeature
iface.openFeatureForm(iface.activeLayer(), QgsFeature(), False)
Layer from WKT
from qgis.core import QgsVectorLayer, QgsFeature, QgsGeometry, QgsProject
layer = QgsVectorLayer('Polygon?crs=epsg:4326', 'Mississippi', 'memory')
pr = layer.dataProvider()
poly = QgsFeature()
geom = QgsGeometry.fromWkt("POLYGON ((-88.82 34.99,-88.0934.89,-88.39 30.34,-89.57 30.18,-89.73 31,-91.63 30.99,-90.8732.37,-91.23 33.44,-90.93 34.23,-90.30 34.99,-88.82 34.99))")
poly.setGeometry(geom)
pr.addFeatures([poly])
layer.updateExtents()
QgsProject.instance().addMapLayers([layer])
Get QSettings list
from qgis.PyQt.QtCore import QgsSettings
qs = QSettings()
for k in sorted(qs.allKeys()):
print (k)
Remove Toolbar
from qgis.utils import iface
toolbar = iface.helpToolBar()
parent = toolbar.parentWidget()
parent.removeToolBar(toolbar)
# and add again
parent.addToolBar(toolbar)
Remove actions toolbar
actions = iface.attributesToolBar().actions()
iface.attributesToolBar().clear()
iface.attributesToolBar().addAction(actions[4])
iface.attributesToolBar().addAction(actions[3])
Remove Menu
from qgis.utils import iface
# for example Help Menu
menu = iface.helpMenu()
menubar = menu.parentWidget()
menubar.removeAction(menu.menuAction())
# and add again
menubar.addAction(menu.menuAction())
https://docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/
https://stackoverflow.com/questions/tagged/qgis