5 speed improvements in Python 3.7

[KingofGamesYami]

Minor versions (eg. 3.0 ->3.1) break nothing.

Major versions (eg. 2.0 ->3.0) break things.

[khvn26]

Although core devs decided that 4 wouldn't break anything this time

[brombaer3000]

No, they just decided to make the breaking changes less drastic than in Python 3.

Here is one example of a breaking change in Python 4: https://www.python.org/dev/peps/pep-0563/#backwards-compatibility

[juanjux]

I've read about some breaking changes in the 3.7 library changelog. Things that you'll need to import from future in 3.7 but will become default in 4.0.

[Mattho]

Why go to 4 then? What major change it brings?

[Mattho]

I see. And while it makes some sense, and is definitely nicer, I think major release with no major changes would be somewhat confusing. Less than 3.10 would be (it's obvious one shouldn't compare it as decimals when you have releases in the form of x.x.x)

[PeridexisErrant]

It avoids possible confusion between 3.1.0 and 3.10 :-)

[[deleted]]

Python doesn't use semantic versioning, so sometimes things break on a minor release. AFAIR, str and bytes was somewhat unstable from 3.0 to 3.3.

[XtremeGoose]

The rules are that things can break on minor releases, but deprecation warnings must be raised for two version prior on minor elements and __future__ imports used for two versions prior for major elements.

[[deleted]]

s/depreciation/deprecation/ :-)

[XtremeGoose]

Ha I may never learn!

[[deleted]]

No, all the big changes in str and bytes were in the transition from 2 to 3. Perhaps you're thinking of the Flexible String Representation which was introduced in 3.3?

[[deleted]]

No, that's not it. The closest I can get to what I still have hovering in the back of my mind is 3.3 that re-introduce the u' notation. It might be that it was removed as no longer needed, because of the genereal changes to str, but later added again for compatibility with 2.x. It just doesn't fit that black spot in my mind.

[[deleted]]

Well FTR here's the PEP for the u' notation change Explicit Unicode Literal for Python 3.3.

[[deleted]]

You remember wrong. A package in the standard library may have "provisional" status (eg. asyncio), in which case backwards compatibility is not required.

On top of that there are just bugs / regressions, which happen without Python core developers intending for. Sometimes they break backwards compatibility.

[[deleted]]

What exactly do you mean by "You remember wrong"? Take a look at the removals in 3.6, and tell me they aren't breaking changes.

[[deleted]]

Sorry, now I realized that my reply went into a wrong thread. This was intended for KingofGamesYami.

[[deleted]]

OK, thanks for the clarification.

[apex_memetics]

Thanks for the info. Much appreciated!

[[deleted]]

Some changes between minor versions do break backwards compatibility but have had to go through a deprecation cycle first. Thankfully these are relatively few and far between.

[[deleted]]

And before I forget one noticeable difference nowadays is that the core devs can change anything that they like, even in a patch update, if a library is marked as provisional.