TOtony·Dec 22, 2019
You can start porting your live codebase to python 3 right now - no downtime at all. You can have a 2+3 compatible codebase live in a week or two, it'll get you about 98% the way there [1]
My projects (e.g. https://tmuxp.git-pull.com, https://unihan-etl.git-pull.com) are both python 2/3 compatible.
I learned by reading through other projects like Sphinx, Flask, Werkzeug, and SQLAlchemy:
- Flask: https://github.com/pallets/flask
- Werkzeug: https://github.com/pallets/werkzeug
- Sphinx https://github.com/sphinx-doc/sphinx/tree/v1.8.5 (see compat: https://github.com/sphinx-doc/sphinx/blob/v1.8.5/sphinx/util...)
- https://github.com/sqlalchemy/sqlalchemy
Helpful blog posts: http://lucumr.pocoo.org/2011/1/22/forwards-compatible-python..., http://lucumr.pocoo.org/2013/5/21/porting-to-python-3-redux/
As for automation tools, for 2/3 compatibili
Read the rest
ty, I used futurize and huge codebase to great success: https://python-future.org/futurize.html. I started with this:
futurize --write --stage1 --unicode-literals --nobackups <files>
and https://docs.python.org/2/library/2to3.html
2to3-2.7 -w -n <files>
Really helped.
Also, wire Travis / your CI system to have your tests run on python 2 and 3.
If you want to test your python 3 codebase live on a subdomain / same SQL/NoSQL DB, be careful about jobs/tasks! Pickle version mismatches and stuff. Use a separate redis/whatever DB for the deployments.
After you're finally on python 3, you can use https://github.com/asottile/pyupgrade to modern your code.
[1] For the other 2%, use conditionals in your requirements file:
enum34==1.0.4;python_version<"3"
ushlex==0.99.1;python_version<"3"