Python - Export MySQL select query results to CSV

Question

Im trying to export MySQL select query results to CSV file .

Im using lambda for this, and my database is in RDS.

I can able to connect and run the queries.

But when I try to save the select query results in CSV format, its not working.

Need python developers help to write this script.

Note: Unicodewritter will not work on lambda.

Lambda function:

import sys
import logging
import rds_config
import pymysql
#rds settings
rds_host  = "connection_link"
name = rds_config.db_username
password = rds_config.db_password
db_name = rds_config.db_name


logger = logging.getLogger()
logger.setLevel(logging.INFO)

try:
    conn = pymysql.connect(rds_host, user=name, passwd=password, db=db_name, connect_timeout=5)
except:
    logger.error("ERROR: Unexpected error: Could not connect to MySql instance.")
    sys.exit()

logger.info("SUCCESS: Connection to RDS mysql instance succeeded")

def handler(event, context):
    """
    This function fetches content from mysql RDS instance
    """

    item_count = 0

    with conn.cursor() as cur:
        cur.execute("create table Employee3 ( EmpID  int NOT NULL, Name varchar(255) NOT NULL, PRIMARY KEY (EmpID))")  
        cur.execute('insert into Employee3 (EmpID, Name) values(1, "Joe")')
        cur.execute('insert into Employee3 (EmpID, Name) values(2, "Bob")')
        cur.execute('insert into Employee3 (EmpID, Name) values(3, "Mary")')
        conn.commit()
        cur.execute("select * from Employee3")

        for row in cur:
            item_count += 1
            logger.info(row)
            #print(row)

Answer 1

The below standard method should work to write all rows :

with conn.cursor() as cur:
    cur.execute("create table Employee3 ( EmpID  int NOT NULL, Name varchar(255) NOT NULL, PRIMARY KEY (EmpID))")  
    cur.execute('insert into Employee3 (EmpID, Name) values(1, "Joe")')
    cur.execute('insert into Employee3 (EmpID, Name) values(2, "Bob")')
    cur.execute('insert into Employee3 (EmpID, Name) values(3, "Mary")')
    conn.commit()
    cur.execute("select * from Employee3")

    res = cur.fetchall()
    with open('output.csv','w') as fileout:
        writer = csv.writer(fileout)
        writer.writerows(res)        

If you need to process lines row by row, you can use the writerow instead :

    cur.execute("select * from Employee3")

    with open('output.csv','w') as fileout:
        writer = csv.writer(fileout)
        for row in cur:
            writer.writerow(row)