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python-3.xgoogle-app-engine

Python 3.7 Local Development Server Options for new app engine apps

I have an app-engine app that is deployed and running on the standard Python3 runtime. I am also able to run it locally using normal commands like flask run. But I am unable to run it the way I could run apps in the 2.7 runtime with dev_appserver.py. I am using the latest gcloud version, but running dev_appserver.py results in:

ERROR: Python 3 and later is not compatible with the Google Cloud SDK. Please use Python version 2.7.x.

I assumed we just aren't supposed to do it this way any more until it saw: https://cloud.google.com/appengine/docs/standard/python3/tools/local-devserver-command

Which starts with:

Python 3.7 Local Development Server Options

Usage:
dev_appserver.py [options] yaml_path [files...]

Is dev_appserver.py compatible with Python3 or not (maybe I somehow have an old version in my path)? If not, is there a new way to run apps locally that will adhere to the app.yaml(like treating static paths correctly) and give other niceties like the local data store that dev_appserver.py provided?

Solution

  • The dev_appserver.py support for Python 3 is still limited. From Running the local development server:

    Note:

    • Running dev_appserver requires the presence of Python 2.7.12+ on your local machine.
    • The updated dev_appserver does not support development of Python 3 apps on Windows.

    Which might be why it is not the recommended solution for local development (or at least not yet). From Running locally:

    We do not recommend that you depend on tools like dev_appserver, the local development server provided with the Google Cloud SDK. However, if you are migrating an existing App Engine application from Python 2 to Python 3, we have updated dev_appserver to facilitate this process. For all other local development scenarios, we recommend standard Python testing approaches.

    For example, you can usually run a Flask application with Flask's development server using:

    python main.py

    Django applications can be started using:

    python manage.py runserver

    To simulate a production App Engine environment, you can run the full Web Server Gateway Interface (WSGI) server locally. To do this, use the same command specified as entrypoint in your app.yaml, for example:

    gunicorn -b :$PORT main:app