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Comment by wpietri | Hacker News Reader

I've recently joined a Python project, my first time working with the language. We're currently using Python 2.7. How do experienced Pythonistas decide if/when to upgrade to 3.x? I figured it was a no brainer given that it has been 7 years with a number of big releases, but Flask's warning on this topic put me off:

http://flask.pocoo.org/docs/0.10/python3/

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Use it by default. If something doesnt work and you cant or dont want to make it work yourself, then fall back and use 2.7.10

P.S. That flask warning is definitely very out of date. I used Flask with Python3 quite happily, literally this week.

Those flask docs look out of date. I don't think you'll hit those troubles in python 3 anymore. It's imo a very mature ecosystem now.

That's very out of date going by: "Python 3 currently has less than 1% of the users of Python 2 going by PyPI download stats." The web ui download starts stopped being updated in 2013 if I remember correctly and api was disabled shortly after due to migration to CDN. So these stats are ~2 years out of date.

I like the "use Python 3 by default, and only use Python 2 if you have mandatory dependencies that aren't 3.x compatible" rule.

IMHO the only reason to use 2.x for new projects is if a necessary dependency doesn't exist for 3 yet.

Sadly the situation for using asyncio for web was not that great last I checked, because that would be a strong incentive.

Using Python 3 in production with Flask here, and been doing so for at least a year now. Never had an issue whatsoever. The warning is frankly outdated.

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