Use a Docker container as a full-featured development environment

Have you ever wanted to try a new programming language but gave up because of all the prerequisites you need to install? Or did you want to make a small change in a (old) project only to find out that you need another version of the programming language than the one currently installed on your PC? With development containers (or dev containers), this can be something of the past.
According to the documentation, a dev container is a Docker container, setup to run an application or to sandbox tools, libraries, and/or runtimes needed for working with a codebase. The Visual Studio Code Remote - Containers extension makes it easy to setup a dev container and use it as a full-featured development environment. Once setup, the configuration files (container definition) can be stored with the other project files in a version control system, so that whenever needed the same development environment can be re-created using the container definition.

Prerequisites

The following software must be installed to use dev containers:

Setup a dev container for a new project

To setup a Python 3 dev container:

Start Visual Studio Code
Open the Command Palette with F1 or Ctrl + Shift + P
In the Command Palette, enter remote container and select Remote Containers: Open Folder in Container...
In the Select Folder dialog, create a new folder for the Python project, select it and click Open
In the Add Development Container Configuration Files dialog, select Show All Definitions...
Enter p and select Python 3
Select a Python version
Select/Unselect Python 3 dev container options. Click Ok to continue.
The following message will be displayed in the Remote Status bar item during the setup of the dev container
When the dev container setup is finished, the following message will be displayed in the Remote Status bar item

In the EXPLORER pane, there is a .devcontainer folder. The files in this folder contains the dev container definition
Open a terminal with Ctrl + \` and enter python --version to verify that you can run python code in the container
Create a Python module to test the debug and run functionality of Visual Studio Code
```
def SayHello(name):
  message = "Hello dev container & " + name
  print(message)

SayHello("docker")
```
Set a breakpoint on line 3 by clicking left of line 3. A red dot will then appear.
Press F5 and select Python File from the Select a debug configuration options to start a debug session.

The debugger executes the module and stops at the breakpoint. In the variables panel, you can see the local variables and their value.
To stop and exit the dev container, click on the Remote Status bar item and select the Close Remote Connection option from the Command palette.

Conclusion

In this article, you have learned how to setup a dev container. There are a large number of predefined container definitions to select from. With dev containers, you can now setup isolated environments to experiment without the fear of polluting your PC.