Intersection

import os
import shutil
 
monCheminDeBase = r'C:\\Users\\georg\\Downloads\\'
 
project = QgsProject.instance()
project.removeAllMapLayers()
project.clear()
iface.mapCanvas().refresh()
 
peaks = QgsVectorLayer(monCheminDeBase + 'peaks_selection/peaks_selection.shp', 'Sommets', 'ogr')
iris = QgsVectorLayer(monCheminDeBase + 'iris/iris.shp', 'IRIS', 'ogr')
 
QgsProject.instance().addMapLayer(peaks)
QgsProject.instance().addMapLayer(iris)
 
# Directory for created layer
_peaks_iris = monCheminDeBase + '_peaks_iris'
if os.path.isdir(_peaks_iris) == True:
    shutil.rmtree(_peaks_iris)
if os.path.isdir(_peaks_iris) == False:
    os.mkdir(_peaks_iris)
 
# Intersect peaks and IRIS
peaks_iris_path = _peaks_iris + r'\\peaks_iris.shp'
 
processing.run('qgis:intersection', { \
"INPUT": peaks, \
"OVERLAY": iris, \
"INPUT_FIELDS": ["OSM_ID", "NAME", "OTHER_TAGS"], \
"OVERLAY_FIELDS": ["CODE_IRIS", "NOM_COM"], \
"OVERLAY_FIELDS_PREFIX": "", \
"OUTPUT": peaks_iris_path})
 
# Remove layers
project.removeMapLayer(peaks)
project.removeMapLayer(iris)
 
# Open the new intersected layer
peaks_iris = QgsVectorLayer(peaks_iris_path, "Sommets", "ogr")
project.addMapLayer(peaks_iris)
 
# Register layer
mes_sommets = project.mapLayersByName("Sommets")[0]

Other params here!