import mysql.connector

db_username='mehdi'
db_password='mehdi'
database_name='cra_db'
db_host='127.0.0.1'

def read_file(filename):
    with open(filename, 'rb') as f:
        photo = f.read()
    return photo

def write_file(data, filename):
    with open(filename, 'wb') as f:
        f.write(data)

def write_blob(author_id, filename):
    # read file
    data = read_file(filename)
    # prepare update query and data
    query = "INSERT INTO `cra_db`.`authors` (`id`,`photo`) VALUES(%s,%s)"
    args = (author_id,data)
    try:
        cnx = mysql.connector.connect(user=db_username, password=db_password, host=db_host, database=database_name)
        cursor = cnx.cursor()
        cursor.execute(query, args)
        cnx.commit()
    except Exception as e:
        print(e)
    finally:
        cursor.close()
        cnx.close()

def update_blob(author_id, filename):
    # read file
    data = read_file(filename)
    # prepare update query and data
    query = "UPDATE authors "
            "SET photo = %s "
            "WHERE id  = %s"
    args = (data, author_id)
    try:
        cnx = mysql.connector.connect(user=db_username, password=db_password, host=db_host, database=database_name)
        cursor = cnx.cursor()
        cursor.execute(query, args)
        cnx.commit()
    except Exception as e:
        print(e)
    finally:
        cursor.close()
        cnx.close()

def read_blob(author_id, filename):
    # select photo column of a specific author
    query = "SELECT photo FROM authors WHERE id = {}".format(author_id)
    try:
        cnx = mysql.connector.connect(user=db_username, password=db_password, host=db_host, database=database_name)
        cursor = cnx.cursor()
        cursor.execute(query)
        out=cursor.fetchall()
        # write blob data into a file
        write_file(out, filename)
    except Exception as e:
        print(e)
    finally:
        cursor.close()
        cnx.close()

def main():
    write_blob(15,"01.jpg")
    update_blob(144, "01.jpg")
    read_blob(144,"02.jpg")

if __name__ == '__main__':
    main()