How to insert object to database mysql using python?

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Python

Python2.4

Raspberry-Pi

Hello I write code read RFID tag using python,check the existence of the ID in the database.
It successfully, right ID on database led is ON, but command insert to database not work. Python no error message, and I do not understand what's wrong with it.
How can I fix it? Please help me. Thank you very much
Here is my code:

import serial
import time
import RPi.GPIO as GPIO
import MySQLdb
from datetime import datetime
from binascii import hexlify
serial=serial.Serial("/dev/ttyAMA0",                    
		      baudrate=9600,                     
                      parity=serial.PARITY_NONE,                    
                      stopbits=serial.STOPBITS_ONE,                    
                      bytesize=serial.EIGHTBITS,
                      timeout=0.1) 
GPIO.setmode(GPIO.BOARD) 
GPIO.setup(12, GPIO.OUT)
chuoi= "\xAA\x00\x03\x25\x26\x00\x00\xBB"
db = MySQLdb.connect(host='localhost', user='root', passwd='root', db='ex_1')
cur = db.cursor(MySQLdb.cursors.DictCursor)
while 1:   
	serial.write(chuoi)      
        data =serial.readline()    
        tach = data[5:8]    
        hex = hexlify(tach)   
        num = int(hex,16)    
        print(num)      
        cur.execute("SELECT * FROM thong_tin WHERE Card_ID = '%d'" %num)    
        rows = cur.fetchall()    
        for row in rows:	
		ID = row['Card_ID']	 	
                if( num == ID):		
			GPIO.output(12, True)
                        cur.execute("INSERT INTO data (Card_ID,Time_out,Time_in) VALUES ('%d',NOW(),NOW())" %num) #-> it does not add to database	
                        time.sleep(3)		
                        GPIO.output(12, False);   	
                else:		
                        GPIO.output(12, False);