Thank you everybody for all pieces of information, very interesting.
I reply to everybody in the same e-mail:
1. For Python 3 usage: Where I work, we switched all new projects to Python 3 since almost one year. To be honest with you, it wasn't to be up-to-date, but it was for a new feature not natively present in Python 2: AsyncIO. We made a lot of Twisted (Telephony+WebSockets) and Django/Flask daemons (WebServices), but I wanted to:
A. Create daemons all-in-one (Telephony+WebSockets+WebServices) to share easier our business logic for a same project.
B. Simplify architecture: Twisted and Django are very complicated for our simple needs.
The side effects are:
A. Our productivity is better, we finish quicker our projects for our clients, because we share more source code and the architecture is simpler to handle.
B. The performances we have are better compare to the past.
Why I tell you that ? To give you a concrete example: if you want to motivate Python developers from the battlefield to migrate to Python 3, you need to add features/performances/... in Python 3. Not add all PyPI libraries in CPython, but add features you can't add easily via a library, like yield from, AsyncIO or Type Hinting.
On production systems, who cares is Python 2/3, Go, Erlang... ? Certainly not clients and even management people. If you want that we use Python 3, please give us arguments to "sell" the migration to Python 3 in the company.
Certainly, some sys admins could be shocked by this behaviour because it's forbidden in packaging religion, but who cares ? We lose less time to deploy, it's more reproducible between dev environment and production, and upgrades are very easy via Ansible.
3. About PyPy usage: I've made some benchmarks with the same WebService between a Flask daemon on PyPy and an AsyncIO daemon on CPython, it was very interesting: Compare to our needs, asynchronous pattern give us more performance that PyPy.
Yes, I know, I've compared apples with pears, but at the end, I only want how many customers I can stack on the same server. More I stack, less it costs for my company.
I'm waiting Python 3.3 support in PyPy to push that on production with a real daemon. No AsyncIO, No PyPy.
4. About Python performance: Two things changed my mind about the bias "Python is slow":
Especially with B.: this benchmark isn't the "truth", but at least, you can compare a lot of languages/frameworks based on examples more closer than my use cases, compare to others benchmarks.
But, for example, if you compare Python frameworks with Erlang frameworks on "multiple queries", you can see that, in fact, Python is very good.
In my mind, Erlang is very complicated to code compare to Python, but you'll have better performances in all cases, I had a wrong opinion.
Finally, everybody has bias about programming languages performance.
5. Type Hinting - Performance booster (the first goal of my e-mail): Thank you Guido, your example is clear.
I understand that it will be step-by-step, it's a good thing. I took the liberty to send an e-mail, because I didn't sure to understand correctly the global roadmap.
I'm the first to understand that it's very difficult, and maybe that CPython will never use Type Hinting to improve performances, because it isn't really simple to implement.
I'm pretty sure I can't help you to implement that, but at least, I can promote to others.
Thank you everybody again for your attention.
Met vriendelijke groeten,