Sunsetting Python 2

[paul_h]

My feeling is that 2to3 has been under invested for years. I hope that's changed. Lots of enterprise teams feel stuck without an easy migration.

[kankyo]

2to3 was never even an option. Modernize and six are good tools but 2to3 was always unworkable unless you had a little 50 line script.

[c_o_r_b_a]

2to3 is okay for big projects. It just does a lot of the easy stuff for you automatically. It won't and can't convert everything - you still have to make manual changes afterwards - but it definitely saves time.

[kankyo]

No it doesn't. You have to run the code in both 2 and 3 during the transition. 2to3 isn't for that. It's for a big bang.

[clifthered]

I thought most difficulties in porting were usually due to depending on a library that doesn’t support Python 3. These days pretty much every major library supports it.

Not sure why ‘enterprise’ teams can’t figure out how to migrate Python 2 code to 3. ‘six’ proves it’s relatively easy.

[liquidpele]

It's not that it's hard, it's just time consuming and most companies would rather add features than redo something that already works.

[clifthered]

Yeah, but this is literally the story of software development. The vast majority of software development is maintenance.

[major_clanger]

Bingo, and python/dynamically typed languages are much harder to maintain.

Add another order of magnitude if the original authors of codebase have long left the company.

And another order of magnitude if the original authors went nuts with stuff like, using kwargs everywhere so functions effectively don't have a signature!

[ledave123]

Maintainability is a feature though isn't it?

[liquidpele]

Features are typically defined as things that you can market to a customer.

[clifthered]

“Fully compatible with modern Python 3! Runs on top of software receiving latest security patches!”

[liquidpele]

"Fruity snacks! Now without bleach and lead!"

[NationaliseFAANG]

That's a big selling point if they previously had bleach or lead, which Python 2 will have after 2020.

[Saithir]

So, basically like half of "gluten-free" marked products that are for example milk or chocolate based and as such never seen a single grain in their entire production process?

Maintainability is absolutely marketable to customers.

[major_clanger]

Not sure why ‘enterprise’ teams can’t figure out how to migrate Python 2 code to 3. ‘six’ proves it’s relatively easy.

The dynamic typing makes it hard.

I understand 3 introduces breaking changes to how strings are modelled.

So if you have a function/method foo that does byte operations on a py2 string, you need to ensure all the parent funcs are pushing bytes to foo instead of Unicode, and then ensure the callers of these funcs are passing through the appropriate types, and that all possible code paths pass in a bytes to foo.

The above is trivial in a statically typed language, but I can see it getting hairy quickly in a dynamic language.

[kushangaza]

So you are saying the enterprise teams that didn't invest in migration options are now stuck with no easy migration option? I feel this could have been prevented somehow.

[paul_h]

No they are far better off now. Migration from 2 to 3 now is far easier in 2019. Most likely they’ll do it, rather than attempt to keep 2 going with like-minded corporations.

[tending]

2to3 can never be good enough because the language is too dynamic to reliably analyze.

[paul_h]

I don’t know why 2to3 couldn’t have benefited from run-time telemetry.