How to Write ETL Logic in Python: Sample Code to Practice

Here's an example Python code that uses the mysql-connector library to connect to a MySQL database, extract data from a table, transform it, and load it as a JSON file. Here's an example:

Python ETL Sample Code

import mysql.connector

import json

# Connect to the MySQL database

cnx = mysql.connector.connect(user='username', password='password',

                              host='localhost',

                              database='database_name')

# Define a cursor to execute SQL queries

cursor = cnx.cursor()

# Define the SQL query to extract data

query = ("SELECT column1, column2, column3 FROM table_name")

# Execute the SQL query

cursor.execute(query)

# Fetch all rows from the result set

rows = cursor.fetchall()

# Transform the rows into a list of dictionaries

result = []

for row in rows:

    result.append({'column1': row[0], 'column2': row[1], 'column3': row[2]})

# Save the result as a JSON file

with open('output.json', 'w') as outfile:

    json.dump(result, outfile)

# Close the cursor and database connection

cursor.close()

cnx.close()

In this example, you will need to replace username, password, localhost, database_name, table_name, column1, column2, and column3 with the appropriate values for your MySQL database and table. 

The code will extract the data from the specified table, transform it into a list of dictionaries, and save it as a JSON file named output.json.