Getting latitude and longitude of lines in attribute table using PyQGIS

I have a road network in form of lines. I retreived the Lat/Long using field calculter in QGIS.

The method I used was:

long: x(centroid($geometry)), for lat y(centroid($geometry))

However, i want to getting the Lat/Long using PyQGIS. The PyQGIS script should automatically add the Lat/Long points in the attribut table of active layer. I tried below script but it is not working.

from qgis.utils import iface

feat = QgsFeature()
mc = iface.mapCanvas()
layer = mc.layer(0)
provider = layer.dataProvider()
provider.select()

while(provider.nextFeature(feat)):
    geometry = feat.geometry()
    print "X Coord %d: " %geometry.asPoint().x()
    print "Y Coord %d: " %geometry.asPoint().y()

lyr = iface.activeLayer()
fl = ['lat','lon'] #Add these fields before executing code

with edit(lyr):
    for f in lyr.getFeatures():
        p = f.geometry().centroid().asPoint()
        _=f.setAttribute(f.fields().indexFromName(fl[0]), p.y())
        _=f.setAttribute(f.fields().indexFromName(fl[1]), p.x())
        _=lyr.updateFeature(f)