Featured Post

Python map() and lambda() Use Cases and Examples

Image
 In Python, map() and lambda functions are often used together for functional programming. Here are some examples to illustrate how they work. Python map and lambda top use cases 1. Using map() with lambda The map() function applies a given function to all items in an iterable (like a list) and returns a map object (which can be converted to a list). Example: Doubling Numbers numbers = [ 1 , 2 , 3 , 4 , 5 ] doubled = list ( map ( lambda x: x * 2 , numbers)) print (doubled) # Output: [2, 4, 6, 8, 10] 2. Using map() to Convert Data Types Example: Converting Strings to Integers string_numbers = [ "1" , "2" , "3" , "4" , "5" ] integers = list ( map ( lambda x: int (x), string_numbers)) print (integers) # Output: [1, 2, 3, 4, 5] 3. Using map() with Multiple Iterables You can also use map() with more than one iterable. The lambda function can take multiple arguments. Example: Adding Two Lists Element-wise list1 = [ 1 , 2 , 3 ]

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.

Comments

Popular posts from this blog

How to Fix datetime Import Error in Python Quickly

SQL Query: 3 Methods for Calculating Cumulative SUM

Python placeholder '_' Perfect Way to Use it