def init__database(self, command, user, password, host, port):
    if command == 'CONNECT':
        try:
            self.db = MySQLdb.connect(host, port=port, user=user, passwd=password)
        except MySQLdb.OperationalError:
            ...

    elif command == 'DISCONNECT':
        # buat fungsi untuk reset form `user, password, host, & port` ke default.
        return self.db.close()

def oke(self, Event=None):
    self.user=self.E_user.get()
    self.password=self.E_passw.get()

    try:
        # disini self.db.cursor() sudah bisa dipake.
        #self.db = MySQLdb.connect("localhost",port=3306, user=self.user, passwd=self.password)#, db="perbankan" )
        self.cursor = self.db.cursor()
        self.showdata.configure(state=NORMAL)
        print 'sukses'
    except MySQLdb.OperationalError:
        ....