Across the land, there are many developers, dev ops, and software delivery managers are terrified of the big move from Python 2.7 to Python 3.6 (at the time of writing this).  You can see all of the versions from the beginning of time.    I am going to walk you through why it is happening, how to plan, and more importantly, how to upgrade your infrastructure in a systematic manner.

Assumptions:

  • There are multiple developers on the team
  • There are multiple Django instances in your organization

Why move? Django

The answer is pretty easy… Django, the core web platform programming framework associated with the Python  programming language won’t support future releases in Python 2.7 any more. In fact, the Django 1.11.x series is the last to support Python 2.7.

Django 2.0 supports Python 3.4, 3.5, and 3.6. We highly recommend and only officially support the latest release of each series.

Note according to PEP 373, Python 2.7 is currently expected to remain supported by the core development team (receiving security updates and other bug fixes) until at least 2020 (10 years after its initial release, compared to the more typical support period of 18–24 months).

How to Plan?

When it comes time to plan for an event like this, it is important that you identify the critical components of your infrastructure.

Sample User Story

As a developer, would like to have a complete list of technical assets that use Python so I can generate an upgrade plan that reduces risk to the company.

Acceptance Criteria: Generate a list of the following assets which include:

  • Your Django platforms to include, dev, test, and production instances.
  • Other internal platforms ( AWS lambdas, small flask instances)
  • External/Internal libraries
  • Cronjob or schedule tasks running Python
  • Continuous Integration systems that build  (ie Jenkins)
  • Unit testing
  • QA regression testing scenarios
  • Code repositories
  • Your development team list (each one of them will have to complete upgrades)

Step 1 – Select Your First System

Pick your first system to do an end to end test.  If you only have one single platform of Django, then… you are done.  We recommend that you clone your dev instance for your first test.  If you don’t have a dev instance, stop reading this and make sure that you do have a dev, test and production version of your platform!

If you have multiple systems, we recommend that you select one that is much smaller in scope and will have as little impact on your operations as possible.

Sample User Story:

As a developer, I would like to select my first computing environment to upgrade Python on so I can minimize the impact on our operations.

Acceptance Criteria:

  • You selected one of the least impactful systems in your eco-systems
  • You clone a working environment that it identical to this instance.
  • You notify the team of what you are doing and discuss any impacts that your testing might have with them.

Step 2 – Start your documentation

If you have other people on the team, you will want to make sure that you can guide them along the path of upgrading their computing environments and be able to discuss problems that you had.

Sample User Story:

As a developer, I would like to document the upgrade process steps that  I took so I can help others on the team upgrade their computing environments to Python 3.6 with Django.

Acceptance Criteria:

  • Document your finding in confluence.

Step 3 – Review external dependencies

Not all pypi libraries are Python 3.6.3 compliant.  Many are only built on Python 2.7.  The good news however, is that most major libraries have been ported to 3.6.x.  The complete list of PyPi libraries per version is listed here.

Individual Library Inspections

As a developer, you can see the details of any pip installed library by calling this command: pip show LIBRARYNAME –verbose

Example:

(bytelion_env)~>pip show requests –verbose
Name: requests
Version: 2.13.0
Summary: Python HTTP for Humans.
Home-page: https://python-requests.org
Author: Kenneth Reitz
Author-email: me@kennethreitz.com
License: Apache 2.0
Location: /Users/terrancemacgregor/.virtualenvs/bytelion_env/lib/python2.7/site-packages
Requires:
Metadata-Version: 2.0
Installer: pip
Classifiers:
Development Status :: 5 – Production/Stable
Intended Audience :: Developers
Natural Language :: English
License :: OSI Approved :: Apache Software License
Programming Language :: Python
Programming Language :: Python :: 2.6
Programming Language :: Python :: 2.7
Programming Language :: Python :: 3
Programming Language :: Python :: 3.3
Programming Language :: Python :: 3.4
Programming Language :: Python :: 3.5
Programming Language :: Python :: 3.6
Programming Language :: Python :: Implementation :: CPython
Programming Language :: Python :: Implementation :: PyPy

Sample User Story

As a developer, I would like to know which PyPi libraries are not supported by my current system so I can determine a migration strategy.

Acceptance Criteria

  • List is generated and shared with the team
  • For each library that is not supported, identify an alternative.

 

Remember the 80/20 rule?

Many of the upgrades from 2.7 to 3.6 can be safely automated, some other changes (notably those associated with Unicode handling) may require careful consideration, and preferably robust automated regression test suites, to migrate effectively.

 

Upgrading Server Code

 

Programming Language :: Python

Here is a list of what some other people experienced:

https://www.calazan.com/upgrading-to-ubuntu-1604-python-36-and-django-111/

https://blog.thezerobit.com/2014/05/25/python-3-is-killing-python.html