Other changes in Python packages

Some low-level improvements have been made in Python since version 3.5, such as faster reading of filesystem directories, automatic retrying of interrupted operating system calls, and a math.isclose function for checking whether two numbers are approximately equal.

There are also a bunch of more minor additions that improve things throughout the standard library, all backwards compatible with earlier Python 3 versions.

In the rare cases where something is added that breaks backwards compatibility, it's not enabled by default. For such a change, if we want to use it, we'd have to specifically mark our code as supporting the change. Those changes will not become standard until two versions later, so a breaking change in Python 3.5 would not become the default until Python version 3.7, with Python 3.5 and 3.6 issuing warnings when they encounter code that depends on the changing feature.

In Python 3.5, there was only one such change-a small and smart alteration in the iteration protocol. It shouldn't have any effect on code that works properly, but technically it's a change in the interface and so it gets the full wait two versions treatment.

If you want more detail about any of these changes I've mentioned, or if you ever want to find out what's changed between versions of Python, the documentation on https://docs.python.org/3/ always contains a what's new document that goes into some detail about new features and provides links to the full documentation.

I always look forward to reading the what's new document for each release of Python, to find out what new toys I've just been handed.

So, we've now taken a high-level view of the Python standard library, introducing us to some of the more useful items it contains. That brings us to the end of our Python primer.