problem inserting unicode value into database

I'm breaking my head with this since yesterday I've done everything to insert the value in utf8 but it is not working and the following I have this code as an example

#!/usr/bin python
# -*- coding: utf-8 -*-

import MySQLdb

db = MySQLdb.connect("localhost", "devel", "********", "Ditados")
cursor = db.cursor()
# cursor.execute("SET NAMES utf8mb4;")
# cursor.execute("SET CHARACTER SET utf8mb4;")
# cursor.execute("SET character_set_connection=utf8mb4;")

autor = u"Desconhecido"
string = u"João e o Pé de Feijão"

sql = "INSERT INTO textos(autor, texto) VALUES ('%s', '%s')" % (autor, string)
cursor.execute(sql)
cursor.fetchone()
db.commit()
db.close()

When I run this script the following error occurs

Warning: Incorrect string value: '\xE3o e o...' for column 'texto' at row 1 cursor.execute(sql)

When I go to see in the database the text is of the following format

MybankandscritareallinUTF8

Can anyone help me get around this problem?