Creating line layer with features using PyQGIS

Question

In QGIS GUI, a line feature is created using this icon

How to create a line with a fixed distance from a vector layer using PyQGIS.

This my example:

from qgis.core import *
from qgis.PyQt.QtCore import QVariant
capa = QgsVectorLayer("Point?crs=epsg:32718", "temp", "memory")
pr = capa.dataProvider()
pr.addAttributes([
                  QgsField("codigo",  QVariant.Int),
                  QgsField("nombre", QVariant.String)])
capa.updateFields() 
...

In Toolbars / mDigitizeToolBar the is action mActionAddFeatures this create a line feature, i need how to call from Python Console, with parameters.

Answer 1

You can add a LineString to a vector layer with PyQGIS 3 with the following code:

# Your code
from qgis.core import *
from qgis.PyQt.QtCore import QVariant
capa = QgsVectorLayer("LineString?crs=epsg:32718", "temp", "memory")
pr = capa.dataProvider()
pr.addAttributes([
                  QgsField("codigo",  QVariant.Int),
                  QgsField("nombre", QVariant.String)])
capa.updateFields()
Add the layer in QGIS project
QgsProject.instance().addMapLayer(capa)
Start editing layer
capa.startEditing()
feat = QgsFeature(capa.fields()) # Create the feature
feat.setAttribute("codigo", 12) # set attributes
feat.setAttribute("nombre", "twelve")
Create HERE the line you want with the 2 xy coordinates
feat.setGeometry(QgsGeometry.fromPolylineXY([QgsPointXY(12, 12),
                                             QgsPointXY(300, 300)]))
capa.addFeature(feat) # add the feature to the layer
capa.endEditCommand() # Stop editing
capa.commitChanges() # Save changes

Note: I had to correct your code where you put Point instead of LineString as the layer geometry type:

capa = QgsVectorLayer("LineString?crs=epsg:32718", "temp", "memory")