Starting on Monday, 12th November, and running through 15th December, Azure App Service hosted on Windows will upgrade all Python sites running Python 3.4.1 to instead run Python 3.6.6. This upgrade will address security vulnerabilities in Python 3.4.1.
The upgrade is an “in place” update and will automatically update the Python binaries currently used by Python 3.4.1 applications. We recommend that customers test existing Python 3.4.1 sites with Python 3.6.6 and make any necessary code changes to ensure that their websites are compatible with the newer Python version.
For more details and to learn how to manually update the Python version in case the site's code is not compatible with Python 3.6.6, see our GitHub announcement.