Remove Dockerfile and VARIANT argument, update README, start using

.devcontainer/devcontainer.json

@@ -1,15 +1,15 @@
 // For format details, see https://aka.ms/devcontainer.json. For config options, see the README at:
 // https://github.com/microsoft/vscode-dev-containers/tree/v0.245.0/containers/python-3
 {
-	"name": "Python 3",
-	"image": "mcr.microsoft.com/vscode/devcontainers/python:3.11-bullseye",
+    "name": "Python 3",
+    "image": "mcr.microsoft.com/devcontainers/python:3.11-bullseye",
 
-	// Configure tool-specific properties.
-	"customizations": {
-		// Configure properties specific to VS Code.
-		"vscode": {
-			// Set *default* container specific settings.json values on container create.
-			"settings": {
+    // Configure tool-specific properties.
+    "customizations": {
+        // Configure properties specific to VS Code.
+        "vscode": {
+            // Set *default* container specific settings.json values on container create.
+            "settings": {
                 "python.defaultInterpreterPath": "/usr/local/bin/python",
                 "python.testing.pytestEnabled": true,
                 "python.testing.unittestEnabled": false,
@@ -18,23 +18,23 @@
                     ".pytest_cache": true,
                     "__pycache__": true
                 }
-			},
+            },
 
-			// Add the IDs of extensions you want installed when the container is created.
-			"extensions": [
-				"ms-python.python",
+            // Add the IDs of extensions you want installed when the container is created.
+            "extensions": [
+                "ms-python.python",
                 "charliermarsh.ruff",
                 "ms-python.black-formatter"
-			]
-		}
-	},
+            ]
+        }
+    },
 
-	// Use 'forwardPorts' to make a list of ports inside the container available locally.
-	// "forwardPorts": [],
+    // Use 'forwardPorts' to make a list of ports inside the container available locally.
+    // "forwardPorts": [],
 
-	// Use 'postCreateCommand' to run commands after the container is created.
-	"postCreateCommand": "pip3 install --user -r requirements-dev.txt && pre-commit install",
+    // Use 'postCreateCommand' to run commands after the container is created.
+    "postCreateCommand": "pip3 install --user -r requirements-dev.txt && pre-commit install",
 
-	// Comment out to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
-	"remoteUser": "vscode"
+    // Comment out to connect as root instead. More info: https://aka.ms/vscode-remote/containers/non-root.
+    "remoteUser": "vscode"
 }

README.md

@@ -11,7 +11,10 @@ It includes `pytest` for testing plus the `pytest-cov` plugin to measure coverag
 
 The checks and tests are all run using Github actions on every pull request and merge to main.
 
-This repository is setup for Python 3.11. To customize that, change the `VARIANT` argument in `.devcontainer/devcontainer.json`, change the config options in `.precommit-config.yaml` and change the version number in `.github/workflows/python.yaml`.
+This repository is setup for Python 3.11. To change the version:
+1. Change the `image` argument in `.devcontainer/devcontainer.json` (see [https://github.com/devcontainers/images/tree/main/src/python](https://github.com/devcontainers/images/tree/main/src/python#configuration) for a list of pre-built Docker images)
+1. Change the config options in `.precommit-config.yaml`
+1. Change the version number in `.github/workflows/python.yaml`
 
 ## Development instructions
 
@@ -55,7 +58,6 @@ Here's a short explanation of each file/folder in this template:
 
 * `.devcontainer`: Folder containing files used for setting up a devcontainer
   * `devcontainer.json`: File configuring the devcontainer, includes VS Code settings
-  * `Dockerfile`: File with commands to build the devcontainer's Docker image
 * `.github`: Folder for Github-specific files and folders
   * `workflows`: Folder containing Github actions config files
     * `python.yaml`: File configuring Github action that runs tools and tests