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Build a Python App with CockroachDB
Learn how to use CockroachDB from a simple Python application with the psycopg2 driver.
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This tutorial shows you how build a simple Python application with CockroachDB using a PostgreSQL-compatible driver or ORM. We've tested and can recommend the Python psycopg2 driver and the SQLAlchemy ORM, so those are featured here.

Before You Begin

Make sure you have already installed CockroachDB.

Step 1. Install the psycopg2 driver

To install the Python psycopg2 driver, run the following command:

$ pip install psycopg2

For other ways to install psycopg2, see the official documentation.

{% include app/common-steps.md %}

Step 5. Run the Python code

Now that you have a database and a user, you'll run code to create a table and insert some rows, and then you'll run code to read and update values as an atomic transaction.

Basic Statements

First, use he following code to connect as the maxroach user and execute some basic SQL statements, creating a table, inserting rows, and reading and printing the rows.

Copy the code or download it directly.

{% include app/basic-sample.py %}

Then run the code:

$ python basic-sample.py

The output should be:

Initial balances:
['1', '1000']
['2', '250']

Transaction (with retry logic)

Next, use the following code to again connect as the maxroach user but this time execute a batch of statements as an atomic transaction to transfer funds from one account to another, where all included statements are either committed or aborted.

Copy the code or download it directly.

{{site.data.alerts.callout_info}}With the default SERIALIZABLE isolation level, CockroachDB may require the client to retry a transaction in case of read/write contention. CockroachDB provides a generic retry function that runs inside a transaction and retries it as needed. You can copy and paste the retry function from here into your code.{{site.data.alerts.end}}

{% include app/txn-sample.py %}

Then run the code:

$ python txn-sample.py

The output should be:

Balances after transfer:
['1', '900']
['2', '350']

However, if you want to verify that funds were transferred from one account to another, use the built-in SQL client:

$ cockroach sql --insecure -e 'SELECT id, balance FROM accounts' --database=bank
+----+---------+
| id | balance |
+----+---------+
|  1 |     900 |
|  2 |     350 |
+----+---------+
(2 rows)

What's Next?

Read more about using the Python psycopg2 driver.

You might also be interested in using a local cluster to explore the following core CockroachDB features: