> ## Documentation Index > Fetch the complete documentation index at: https://cockroachlabs.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Build a Python App with CockroachDB and asyncpg export const InternalLink = ({version, path = "", children, ...props}) => { let detectedVersion = version || "stable"; if (typeof window !== 'undefined' && !version) { const match = window.location.pathname.match(/\/docs\/([^/]+)/); if (match) { detectedVersion = match[1]; } } const normalizedPath = path.startsWith("/") ? path.slice(1) : path; return {children} ; }; export const InternalLink = ({version, path = "", children, ...props}) => { let detectedVersion = version || "stable"; if (typeof window !== 'undefined' && !version) { const match = window.location.pathname.match(/\/docs\/([^/]+)/); if (match) { detectedVersion = match[1]; } } const normalizedPath = path.startsWith("/") ? path.slice(1) : path; return {children} ; }; Check out our developer courses at [Cockroach University](https://university.cockroachlabs.com/). This tutorial shows you how build a simple Python application with CockroachDB and the [asyncpg](https://magicstack.github.io/asyncpg/current/index.html) driver. ## Step 1. Start CockroachDB ### Choose your installation method You can create a CockroachDB Basic cluster using either the CockroachDB Cloud Console, a web-based graphical user interface (GUI) tool, or `ccloud`, a command-line interface (CLI) tool. ### Create a free cluster Organizations without billing information on file can only create one CockroachDB Basic cluster. 1. If you haven't already, [sign up for a CockroachDB Cloud account](https://cockroachlabs.cloud/signup?referralId=docs_python_asyncpg). 2. [Log in](https://cockroachlabs.cloud/) to your CockroachDB Cloud account. 3. On the **Clusters** page, click **Create cluster**. 4. On the **Select a plan** page, select **Basic**. 5. On the **Cloud & Regions** page, select a cloud provider (GCP or AWS) in the **Cloud provider** section. 6. In the **Regions** section, select a region for the cluster. Refer to CockroachDB Cloud Regions for the regions where CockroachDB Basic clusters can be deployed. To create a multi-region cluster, click **Add region** and select additional regions. 7. Click **Next: Capacity**. 8. On the **Capacity** page, select **Start for free**. Click **Next: Finalize**. 9. On the **Finalize** page, click **Create cluster**. Your cluster will be created in a few seconds and the **Create SQL user** dialog will display. ### Create a SQL user The **Create SQL user** dialog allows you to create a new SQL user and password. 1. Enter a username in the **SQL user** field or use the one provided by default. 2. Click **Generate & save password**. 3. Copy the generated password and save it in a secure location. 4. Click **Next**. Currently, all new SQL users are created with admin privileges. For more information and to change the default settings, see Manage SQL users on a cluster. ### Get the root certificate The **Connect to cluster** dialog shows information about how to connect to your cluster. 1. Select **General connection string** from the **Select option** dropdown. 2. Open a new terminal on your local machine, and run the **CA Cert download command** provided in the **Download CA Cert** section. The client driver used in this tutorial requires this certificate to connect to CockroachDB Cloud. ### Get the connection string Open the **General connection string** section, then copy the connection string provided and save it in a secure location. The connection string is pre-populated with your username, password, cluster name, and other details. Your password, in particular, will be provided *only once*. Save it in a secure place (Cockroach Labs recommends a password manager) to connect to your cluster in the future. If you forget your password, you can reset it by going to the **SQL Users** page for the cluster, found at `https://cockroachlabs.cloud/cluster//users`. Follow these steps to create a CockroachDB Basic cluster using the `ccloud` CLI tool. The `ccloud` CLI tool is in Preview. ### Install `ccloud` You can install `ccloud` using either Homebrew or by downloading the binary. #### Use Homebrew 1. [Install Homebrew](http://brew.sh/). 2. Install using the `ccloud` tap: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} brew install cockroachdb/tap/ccloud ``` #### Download the binary In a terminal, enter the following command to download and extract the `ccloud` binary and add it to your `PATH`: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} curl https://binaries.cockroachdb.com/ccloud/ccloud_darwin-amd64_.tar.gz | tar -xJ && cp -i ccloud /usr/local/bin/ ``` Use the ARM 64 binary if you have an M-series Mac: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} curl https://binaries.cockroachdb.com/ccloud/ccloud_darwin-arm64_.tar.gz | tar -xJ && cp -i ccloud /usr/local/bin/ ``` In a terminal, enter the following command to download and extract the `ccloud` binary and add it to your `PATH`: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} curl https://binaries.cockroachdb.com/ccloud/ccloud_linux-amd64_.tar.gz | tar -xz && cp -i ccloud /usr/local/bin/ ``` In a PowerShell window, enter the following command to download and extract the `ccloud` binary and add it to your `PATH`: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ErrorActionPreference = "Stop"; [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; $ProgressPreference = 'SilentlyContinue'; $null = New-Item -Type Directory -Force $env:appdata/ccloud; Invoke-WebRequest -Uri https://binaries.cockroachdb.com/ccloud/ccloud_windows-amd64_.zip -OutFile ccloud.zip; Expand-Archive -Force -Path ccloud.zip; Copy-Item -Force ccloud/ccloud.exe -Destination $env:appdata/ccloud; $Env:PATH += ";$env:appdata/ccloud"; # We recommend adding ";$env:appdata/ccloud" to the Path variable for your system environment. See https://docs.microsoft.com/powershell/module/microsoft.powershell.core/about/about_environment_variables#saving-changes-to-environment-variables for more information. ``` ### Run `ccloud quickstart` to create a new cluster, create a SQL user, and retrieve the connection string. The easiest way of getting started with CockroachDB Cloud is to use `ccloud quickstart`. The `ccloud quickstart` command guides you through logging in to CockroachDB Cloud, creating a new CockroachDB Basic cluster, and connecting to the new cluster. Run `ccloud quickstart` and follow the instructions: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} ccloud quickstart ``` The `ccloud quickstart` command will open a browser window to log you in to CockroachDB Cloud. If you are new to CockroachDB Cloud, you can register using one of the single sign-on (SSO) options, or create a new account using an email address. The `ccloud quickstart` command will prompt you for the cluster name, cloud provider, and cloud provider region, then ask if you want to connect to the cluster. Each prompt has default values that you can select, or change if you want a different option. Select **General connection string**, then copy the connection string displayed and save it in a secure location. The connection string is the line starting `postgresql://`. ``` ? How would you like to connect? General connection string Retrieving cluster info: succeeded Downloading cluster cert to /Users/maxroach/.postgresql/root.crt: succeeded postgresql://maxroach:ThisIsNotAGoodPassword@blue-dog-147.6wr.cockroachlabs.cloud:26257/defaultdb?sslmode=verify-full&sslrootcert=%2FUsers%2Fmaxroach%2F.postgresql%2Froot.crt ``` 1. If you haven't already, download the CockroachDB binary. 2. Run the `cockroach start-single-node` command: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ cockroach start-single-node --advertise-addr 'localhost' --insecure ``` This starts an insecure, single-node cluster. 3. Take note of the following connection information in the SQL shell welcome text: ``` CockroachDB node starting at 2021-08-30 17:25:30.06524 +0000 UTC (took 4.3s) build: CCL v21.1.6 @ 2021/07/20 15:33:43 (go1.15.11) webui: http://localhost:8080 sql: postgresql://root@localhost:26257?sslmode=disable ``` You'll use the `sql` connection string to connect to the cluster later in this tutorial. The `--insecure` flag used in this tutorial is intended for non-production testing only. To run CockroachDB in production, use a secure cluster instead. ## Step 2. Get the sample code Clone the sample code's GitHub repo: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ git clone https://github.com/cockroachdb/example-app-python-asyncpg ``` The sample code in `example.py` does the following: * Creates an `accounts` table and inserts some rows * Transfers funds between two accounts inside a transaction * Deletes the accounts from the table before exiting so you can re-run the example code To handle transaction retry errors, the code uses an application-level retry loop that, in case of error, sleeps before trying the funds transfer again. If it encounters another retry error, it sleeps for a longer interval, implementing [exponential backoff](https://wikipedia.org/wiki/Exponential_backoff). ## Step 3. Install the asyncpg driver `asyncpg` is the sample app's only third-party module dependency. To install `asyncpg`, run the following command: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ pip3 install "asyncpg" ``` For other ways to install Psycopg, see the [official documentation](https://www.psycopg.org/psycopg3/docs/basic/install.html). ## Step 4. Run the code 1. Set the `DATABASE_URL` environment variable to the connection string to your cluster: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ export DATABASE_URL="postgresql://root@localhost:26257/defaultdb?sslmode=disable" ``` ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ export DATABASE_URL="{connection-string}" ``` Where {'{connection-string}'} is the connection string you copied earlier. The app uses the connection string saved to the `DATABASE_URL` environment variable to connect to your cluster and execute the code. 1. Run the code: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ cd example-app-python-asyncpg ``` ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ python3 example.py ``` The output should show the account balances before and after the funds transfer: ``` Balances at Thu Aug 4 15:51:03 2022: account id: 2e964b45-2034-49a7-8ab8-c5d0082b71f1 balance: $1000 account id: 889cb1eb-b747-46f4-afd0-15d70844147f balance: $250 Balances at Thu Aug 4 15:51:03 2022: account id: 2e964b45-2034-49a7-8ab8-c5d0082b71f1 balance: $900 account id: 889cb1eb-b747-46f4-afd0-15d70844147f balance: $350 ``` The example code sets the `multiple_active_portals_enabled` session variable to `true`, a requirement for using `asyncpg` with CockroachDB. ## What's next? Read more about using the [asyncpg](https://magicstack.github.io/asyncpg/current/usage.html). You might also be interested in the following pages: * [Client Connection Parameters](connection-parameters) * [Connection Pooling](connection-pooling) * [Data Replication](demo-replication-and-rebalancing) * [CockroachDB Resilience](demo-cockroachdb-resilience) * [Replication & Rebalancing](demo-replication-and-rebalancing)