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Try Out Development Containers: Python

A development container is a running container with a well-defined tool/runtime stack and its prerequisites. You can try out development containers with GitHub Codespaces or Visual Studio Code Dev 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-* sample projects, too.

Note: If you already have a codespace or dev container, you can jump to the Things to try section.

Setting up the development container

GitHub Codespaces

Follow these steps to open this sample in a Codespace:

Click the Code drop-down menu.
Click on the Codespaces tab.
Click Create codespace on main .

For more information on creating your codespace, visit the GitHub documentation.

VS Code Dev Containers

If you already have VS Code and Docker installed, you can click the badge above or here to get started. Clicking these links will cause VS Code to automatically install the Dev Containers extension if needed, clone the source code into a container volume, and spin up a dev container for use.

Follow these steps to open this sample in a container using the VS Code Dev Containers extension:

If this is your first time using a development container, please ensure your system meets the prerequisites (i.e. have Docker installed) in the getting started steps.
To use this repository, you can either open the repository in an isolated Docker volume:
- Press <kbd>F1</kbd> and select the Dev Containers: Try a Sample... command.
- Choose the "Python" sample, wait for the container to start, and try things out!
  
  Note: Under the hood, this will use the Dev Containers: Clone Repository in Container Volume... command to clone the source code in a Docker volume instead of the local filesystem. Volumes are the preferred mechanism for persisting container data.
Or open a locally cloned copy of the code:
- Clone this repository to your local filesystem.
- Press <kbd>F1</kbd> and select the Dev Containers: Open Folder in Container... command.
- Select the cloned copy of this folder, wait for the container to start, and try things out!

Things to try

Once you have this sample opened, you'll be able to work with it like you would locally.

Some things to try:

Edit:
- Open app.py
- Try adding some code and check out the language features.
- Make a spelling mistake and notice it is detected. The Code Spell Checker extension was automatically installed because it is referenced in .devcontainer/devcontainer.json.
- Also notice that utilities like pylint and the Python extension are installed. Tools are installed in the mcr.microsoft.com/devcontainers/python image and Dev Container settings and metadata are automatically picked up from image labels.
Terminal:
- Press <kbd>ctrl</kbd>+<kbd>shift</kbd>+<kbd>`</kbd> to open a terminal window.
- Type python -m flask run --port 9000 --no-debugger --no-reload to run the app.
  - The terminal will say your app is Running on http://127.0.0.1:9000/. Click on the link in the terminal to view your app running in the browser.
- 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.
Build, Run, and Debug:
- Open app.py
- Add a breakpoint (e.g. on line 9).
- Press <kbd>F5</kbd> to launch the app in the container.
- Once the breakpoint is hit, try hovering over variables (e.g. the app variable on line 7), examining locals, and more.
- Continue (<kbd>F5</kbd>). You can connect to the server in the container by either:
  - Clicking on Open in Browser in the notification telling you: Your service running on port 9000 is available.
  - Clicking the globe icon in the 'Ports' view. The 'Ports' view gives you an organized table of your forwarded ports, and you can access it with the command Ports: Focus on Ports View.
- Notice port 9000 in the 'Ports' view is labeled "Hello Remote World." In devcontainer.json, you can set "portsAttributes", such as a label for your forwarded ports and the action to be taken when the port is autoforwarded.
Note: In Dev Containers, you can access your app at http://localhost:9000 in a local browser. But in a browser-based Codespace, you must click the link from the notification or the Ports view so that the service handles port forwarding in the browser and generates the correct URL.
Rebuild or update your container

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.

Open browser automatically: As an example change, let's update the portsAttributes in the .devcontainer/devcontainer.json file to open a browser when our port is automatically forwarded.
- Open the .devcontainer/devcontainer.json file.
- Modify the "onAutoForward" attribute in your portsAttributes from "notify" to "openBrowser".
- Press <kbd>F1</kbd> and select the Dev Containers: Rebuild Container or Codespaces: Rebuild Container command so the modifications are picked up.
Install Node.js using a Dev Container Feature:
- Press <kbd>F1</kbd> and select the Dev Containers: Configure Container Features... or Codespaces: Configure Container Features... command.
- Type "node" in the text box at the top.
- Check the check box next to "Node.js (via nvm) and yarn" (published by devcontainers)
- Click OK
- Press <kbd>F1</kbd> and select the Dev Containers: Rebuild Container or Codespaces: Rebuild Container command so the modifications are picked up.

More samples

Tweeter App - Python and Django

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.