A basic Python demo CRUD application using the DataStax Python Driver for Apache Cassandra. Run the quickstart_complete.py file if you want to skip the exercise and run the application with the complete code.

Contributors: Rebecca Mills

Objectives

  • To demonstrate how to perform basic CRUD operations with the DataStax Python Driver.
  • The intent is to help users get up and running quickly with the driver.

How this Sample Works

This project walks through basic CRUD operations using Cassandra. The demo application will first insert a row of user data, select that same row back out, update the row and finally delete the user. The README includes the code snippets to be filled in to the main application code to complete the functionality.

Project Layout

  • quickstart.py - main application file with space to fill in CRUD operation code
  • users.cql - Use this file to create the schema

Prerequisites

  • A running instance of Apache Cassandra┬« 2.1+
  • Python 2.7, 3.4, 3.5, or 3.6.
  • Use Pip to install the driver: pip install cassandra-driver
  • We highly recommend to use a virtualenv

Create the keyspace and table

The users.cql file provides the schema used for this project:

CREATE KEYSPACE demo
    WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '1'};
CREATE TABLE demo.users (
    lastname text PRIMARY KEY,
    age int,
    city text,
    email text,
    firstname text);

Connect to your cluster

All of our code is contained in the quickstart.py file. The create_connection() function connects to our cluster. By default, Cluster() will try to connect to 127.0.0.1 (localhost). Replace with your own contact point(s) if necessary.

def create_connection():
    # TO DO: Fill in your own contact point
    cluster = Cluster(['127.0.0.1'])
    return cluster.connect('demo')

CRUD Operations

Fill the code in the functions that will add a user, get a user, update a user and delete a user from the table with the driver.

INSERT a user

def set_user(session, lastname, age, city, email, firstname):
    # TO DO: execute SimpleStatement that inserts one user into the table
    session.execute("INSERT INTO users (lastname, age, city, email, firstname) VALUES (%s,%s,%s,%s,%s)", [lastname, age, city, email, firstname])

SELECT a user

def get_user(session, lastname):
    # TO DO: execute SimpleStatement that retrieves one user from the table
    # TO DO: print firstname and age of user
    result = session.execute("SELECT * FROM users WHERE lastname = %s", [lastname]).one()
    print result.firstname, result.age

UPDATE a user's age

def update_user(session, new_age, lastname):
    # TO DO: execute SimpleStatement that updates the age of one user
    session.execute("UPDATE users SET age =%s WHERE lastname = %s", [new_age, lastname])

DELETE a user

def delete_user(session, lastname):
    # TO DO: execute SimpleStatement that deletes one user from the table
    session.execute("DELETE FROM users WHERE lastname = %s", [lastname])

License

Copyright 2019 Rebecca Mills

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.