Python’s development is communicated through a myriad of ways, mostly through mailing lists, but also other forms.
The primary mailing list where discussions about Python’s development occur is python-dev. The list is open to the public and is subscribed to by all core developers plus many people simply interested in following Python’s development. Discussion is focused on issues related to Python’s development, such as how to handle a specific issue, a PEP, etc. Ideas about new functionality should not start here and instead should be sent to python-ideas. Technical support questions should also not be asked here and instead should go to python-list or python-help.
The python-committers mailing list is a private mailing list for core developers (the archives are publicly available). If something only affects core developers (e.g., the tree is frozen for commits, etc.), it is discussed here instead of python-dev to keep traffic down on the latter.
Python-checkins sends out an email for every commit to Python’s various repositories from http://hg.python.org. All core developers subscribe to this list and are known to reply to these emails to make comments about various issues they catch in the commit. Replies get redirected to python-dev.
There are two mailing lists related to issues on the issue tracker. If you only want an email for when a new issue is open, subscribe to new-bugs-announce. If you would rather receive an email for all changes made to any issue, subscribe to python-bugs-list.
Sometimes people post new ideas to python-list to gather community opinion before heading to python-ideas. The list is also sometimes known as comp.lang.python, the name of the newsgroup is mirrors (it is also known by the abbreviation c.l.py).
A complete list of Python mailing lists can be found at http://mail.python.org. Most lists are also mirrored at http://news.gmane.org/ and can be read and posted to in various ways, including via web browsers, NNTP newsreaders, and RSS feed readers.
Some core developers enjoy spending time on IRC discussing various issues regarding Python’s development in the #python-dev channel on irc.freenode.net. This is not a place to ask for help with Python, but to discuss issues related to Python’s own development. You can use freenode’s Web interface if you don’t have an IRC client.