How do you set the debugpy launcher to use python3?

[dwbelliston]

https://github.com/microsoft/vscode-docker/blob/master/resources/python/launcher.py

This file has a section of args that are passed to docker exec.

dockerExecArgs = ['docker', 'exec', '-d', containerId, 'python', '/debugpy/launcher'] + args

My debug fails, because the container receives python as python2.7, but my program needs python3, which is available in the container. If i change this launcher.py file to python3 it works. Can i pass this somehow to the launcher?

[bwateratmsft]

@dwbelliston What Python base image are you using? I'm surprised there are any where python maps to Python2.7...

[dwbelliston]

Here is the dockerfile and launch.json.

The base image from docker file is here: https://hub.docker.com/r/google/cloud-sdk/dockerfile

Dockerfile:

# https://github.com/GoogleCloudPlatform/cloud-sdk-docker
# Image provides: gcloud, gsutil, bq, python and more
FROM gcr.io/google.com/cloudsdktool/cloud-sdk:latest

COPY requirements.txt /opt/src/
RUN pip3 install -r /opt/src/requirements.txt

COPY src/ /opt/src

WORKDIR /opt/src/

CMD ["python3", "main.py"]

launch.json

    {
      "name": "Docker:Raw",
      "type": "docker",
      "request": "launch",
      "preLaunchTask": "docker-run:raw",
      "platform": "python",
      "python": {
        "pathMappings": [
          {
            "localRoot": "${workspaceFolder}/raw/src",
            "remoteRoot": "/opt/src"
          }
        ],
        "projectType": "general"
      }
    }

[bwateratmsft]

Thanks! It looks like that image indeed uses 2.7 as the default. I think we can safely change launcher.py in our extension to use python3 since that works on python:3.8-slim-buster as expected.

As a workaround before we can get that fixed, you can make the same change to launcher.py in the Docker extension's resources.

Windows: %USERPROFILE%\.vscode\extensions\ms-azuretools.vscode-docker-1.3.1\resources\python\launcher.py
Mac/Linux: ~/.vscode/extensions/ms-azuretools.vscode-docker-1.3.1/resources/python/launcher.py

Change python to python3 in dockerExecArgs on line 17.

Alternatively, you could make a copy of that file and use the debugLauncherPath property in the launch config, but that's probably more work.

[bwateratmsft]

We have released Docker 1.4.0 which contains a fix for this.