polygon - Saving centroid with attribute fields in PyQGIS?

I'm new in PyQGIS and wrote a script to read a polygon and get the centroid:

from qgis.PyQt.QtGui import *
from qgis.PyQt.QtCore import *

# insert the location of the shp
layer = iface.addVectorLayer("/media/path/Setor_Censit_Urb_Cast_2010.shp", "Setor", "ogr")
layer2 = QgsVectorLayer('Point?crs=epsg:4326', 'MyPoint' , 'memory')


pts = [] 

# save the centroid as vector
prov = layer2.dataProvider()
points = []
for feature in layer.getFeatures():
    geometry = feature.geometry()
    centroid = geometry.centroid().asPoint()
    pts = [centroid]

    name = feature.attribute("CD_GEOCODI") # select the attribute

# Insert the coordinates in the layer2 shapefile
    for x,y in pts:
            feat = QgsFeature()
            point = QgsPoint(x,y)
            feat.setGeometry(QgsGeometry.fromPoint(point))
            points.append(feat)
prov.addFeatures(points)


# update extent of the layer
layer2.updateExtents()

# add the layer to the layers panel
QgsMapLayerRegistry.instance().addMapLayers([layer2])

But I want the attributes too. How can I do it?

Answer

It's not completely clear which datatype the attribute should have. I am assuming string here (but it could be int or double among others as well).

The code below also has been simplified and shortened:

1. There is no need to convert from the centroid to point to x and y and back. Just use the centroid geometry directly.


2. Do not use the dataProvider. Just use the methods on the layer.


3. No need to loop over an array with a single entry in it (The pts array).

---

source_layer = iface.addVectorLayer("/media/path/Setor_Censit_Urb_Cast_2010.shp", "Setor", "ogr")

# Define additional attributes already on the layer level
centroid_layer = QgsVectorLayer('Point?crs=epsg:4326&field=cd_geocodi:string', 'MyPoint' , 'memory')


centroid_layer.startEditing()
# Loop over all features
for source_feature in source_layer.getFeatures():
    geometry = source_feature.geometry()
    centroid = geometry.centroid()
    name = source_feature.attribute("CD_GEOCODI")
    # or use source_feature['CD_GEOCODI']

    # Create the new feature with the fields of the memory layer

    # And set geometry and attribute before adding it to the target layer
    centroid_feature = QgsFeature(source_layer.fields())
    centroid_feature.setGeometry(centroid)
    centroid_feature['cd_geocodi'] = name
    centroid_layer.addFeature(centroid_feature)

centroid_layer.commitChanges()

# Add the layer to the registry
QgsMapLayerRegistry.instance().addMapLayer(centroid_layer)

Further note, do not use * imports. They are a bad habit and will bite you when you want to upgrade your script to QGIS 3.

from qgis.PyQt.QtGui import QSomethingYouUse
from qgis.PyQt.QtCore import QWhateverElseYouReallyNeed