Récupérer la valeur d'un enregistrement sqlite dans un textbox en PyQt5

from PyQt5.QtCore import *
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
import sys
import sqlite3
class Fenetre(QMainWindow):
        def __init__(self):
            super(Fenetre, self).__init__()
            self.setWindowTitle("Mon interface")
            self.setMinimumSize(100,200)
            self.setWindowIcon(QIcon("icon.png"))

            #Création du combobox:
            self.combobox=QComboBox(self)
            #self.combobox.addItem(self.requete())
            self.combobox.move(40,40)
            self.combobox.addItem("enregistrement à récupérer")



app=QApplication.instance()
if not app:
    app=QApplication(sys.argv)
fenetre=Fenetre()
fenetre.show()
app.exec_()

    def requete(self):
            xcon = sqlite3.connect("mabase.db")
            xcur = xcon.cursor()
            xcur.execute("create table if not exists user(id integer,nom string(25))")
            xcur.execute("insert into user(id,nom) values(1,"Julien")")
            xcur.execute("insert into user(id,nom) values(2,"José")")
            xcur.execute("insert into user(id,nom) values(3,"Francois")")
            print(xcur.fetchall())
            liste=xcur.fetchall()
            xcon.commit()
            xcon.close()