Python 3.7.2 and 3.6.8 are now available (opens in new tab)

Per the 3.6 release schedule[1], 3.6 was the stable branch until the final release of 3.7.0. After that, it was to receive two more bug fix releases and then switch over to security fixes. 3.7.0 final was released a few months ago, so this is the last bugfix release for 3.6.x. 3.7.0 is now considered "stable". However, 3.6.8 will still receive security fixes for anyone that is depending on it.

This is generally done for those who want "stable" releases with minimal bug fixes. The 3.7 branch has newer features and therefore, potentially more bugs.

If you want the latest stable version, get 3.7.0. If you want the latest version, get 3.7.2.

[1] https://www.python.org/dev/peps/pep-0494/

Well, as described in the OC 3.6.8 is a bugfix release for the 3.6 branch. Whoever needs to ensure compatibility with the featureset of 3.6 and not risk incompatibilities with 3.7 but wants bugfixes would use the latest 3.6.

Everybody interested in the new features from 3.7 would use the latest version here.

As python can introduce minor "breaking" changes this is quite a good way of ensuring compatibility.

From the announcement in the linked page:

>> Python 3.6.8 is planned to be the last bugfix release of Python 3.6. Per our support policy, we plan to provide security fixes for Python 3.6 as needed through 2021, five years following its initial release.

For a new project you definitely want to use Python 3 as Python will be EOL in 2020.

For new projects I tend to favor Python 3.7 over 3.6. But sometimes I have to fall back to 3.6 because some packages have not been updated yet and I don't want to install them from Git(Hub) (e.g. GeoPandas through pyproj).

Choose the latest 3.x release, unless you have some dependencies that don't work with the latest release (yet).

There are differences between 3.x releases, and things like security issues or bugs need to be fixed. Saying "well duh just upgrade" isn't acceptable.

A major library I use doesn’t work on 3.7 yet, so still stuck on 3.6. It’s sure nice to get bug fixes and security while I wait for the PR of my library to get merged.

Very rare everyone can jump versions especially when there are syntax changes. In my case it’s around imports.

I think exactly the same. The only reasons I can imagine are that perhaps a feature can happen to be deprecated between these releases and the internals of the implementation of a particular part can change significantly and this can lead to notable change in performance of a particular algorithm some production service may rely on. As for the right choice for a fresh project - IMHO it's always the latest working version available, even a beta as long as everything you need works fine in it.

This doesn't invalidate your question, but an interesting comparison: Historically the same situation of fairly regular minor releases was the norm, even for Python 2.x. It was only when Python 3 was released that Python 2.x was fixed on Python 2.7 for a while (for a generous definition of "a while"), so that was the anomaly.

> But what is the rationale for maintaining multiple 3.x branches?

Introducing new features bears an elevated risk of breaking thingss. Hence stable systems (and in extension, stable distributions like Debian) tend to use stable, bug and security fix only branches. This used to be more common.

Just to clarify. This behavior is expected since 3.6:

As of Python 3.6, for the CPython implementation of Python, dictionaries remember the order of items inserted. This is considered an implementation detail in Python 3.6; you need to use OrderedDict if you want insertion ordering that's guaranteed across other implementations of Python.

As of Python 3.7, this is no longer an implementation detail and instead becomes a language feature.

[1] https://stackoverflow.com/questions/39980323/are-dictionarie...

> Dicts now retain order now (in other words all dicts are ordered dicts).

I think you can be more clear here: all dicts are ordered by insertion order (not by key).

It's a surprisingly useful feature.

I am responsible for maitaining a Python 3.4 asyncio app at work, and recently in charge of building a new (not replacing) system in 3.7. The difference is truly enormous in a very pleasant way.