from qgis.core import *
import qgis.utils
from qgis.PyQt.QtCore import QVariant
fields = QgsFields()
fields.append(QgsField("ID", QVariant.Int))
fields.append(QgsField("size", QVariant.Double))
fields.append(QgsField("name", QVariant.String))
fields.append(QgsField("okoli", QVariant.Int))
writer= QgsVectorFileWriter("/Users/karst/Downloads/t1.shp","CP1250",fields,QgsWkbTypes.Point,QgsCoordinateReferenceSystem(),"ESRI Shapefile")
o=iface.activeLayer().getFeatures()
n=0
ob=[]
for i in o:
    ob.append(i)
for i in ob:
    obec = i.geometry()
    fet = QgsFeature()
    fet.setGeometry(obec.centroid())
    fet.setAttributes([n,i["POCET_OBYV"],i["NAZ_OBEC"]])
    n=n+1
    writer.addFeature(fet)
del writer