A **development container** is a running [Docker](https://www.docker.com) container with a well-defined tool/runtime stack and its prerequisites. You can try out development containers with **[GitHub Codespaces](https://github.com/features/codespaces)** or **[Visual Studio Code Remote - Containers](https://aka.ms/vscode-remote/containers)**.
This is a sample project that lets you try out either option in a few easy steps. We have a variety of other [vscode-remote-try-*](https://github.com/search?q=org%3Amicrosoft+vscode-remote-try-&type=Repositories) sample projects, too.
Follow these steps to open this sample in a Codespace:
1. Click the Code drop-down menu and select the **Open with Codespaces** option.
1. Select **+ New codespace** at the bottom on the pane. If you don't own the repo, this will create a fork of this repository under your account.
For more info, check out the [GitHub documentation](https://docs.github.com/en/free-pro-team@latest/github/developing-online-with-codespaces/creating-a-codespace#creating-a-codespace).
### VS Code Remote - Containers
Follow these steps to open this sample in a container using the VS Code Remote - Containers extension:
1. If this is your first time using a development container, please ensure your system meets the pre-reqs (i.e. have Docker installed) in the [getting started steps](https://aka.ms/vscode-remote/containers/getting-started).
- Choose the "Python" sample, wait for the container to start, and try things out!
> **Note:** Under the hood, this will use the **Remote-Containers: Clone Repository in Container Volume...** command to clone the source code in a Docker volume instead of the local filesystem. [Volumes](https://docs.docker.com/storage/volumes/) are the preferred mechanism for persisting container data.
> **Note:** This container runs as a non-root user with sudo access by default. Comment out `"remoteUser": "vscode"` in `.devcontainer/devcontainer.json` if you'd prefer to run as root.
- Notice that the Python extension is already installed in the container since the `.devcontainer/devcontainer.json` lists `"ms-python.python"` as an extension to install automatically when the container is created.
> **Tip:** If you use this container outside of VS Code via `docker run` with `-p 9000`, you may need to append `--host 0.0.0.0` to the command above. The `-p` option "publishes" the port rather than forwarding it. It therefore will not work if the application only listens to localhost. The `forwardPorts` property in `devcontainer.json` does not have this limitation, but you can use `appPort` property instead if you want to mirror the `docker run` behavior.
4.**Rebuild or update your container** (*Currently, only containers with the VS Code Remote - Containers extension can be rebuilt.*)
You may want to make changes to your container, such as installing a different version of a software or forwarding a new port. You'll rebuild your container for your changes to take effect.
**Forward a port statically:** As an example change, let's forward a port statically in the `.devcontainer/devcontainer.json` file.
> **Note:** Remote-Containers and Codespaces also take care of dynamic port forwarding, but there may be instances in which we want to statically declare a forwarded port.
- Open the `.devcontainer/devcontainer.json` file.
- Uncomment the `forwardedPorts` attribute and adjust the port number as needed.
- Press <kbd>F1</kbd> and select the **Remote-Containers: Rebuild Container** command so the modifications are picked up.
