On behalf of the Python development community and the Python 3.5 release team, I'm surprised to announce the availability of Python 3.5.0rc4, also known as Python 3.5.0 Release Candidate 4.

Python 3.5.0 Release Candidate 3 was only released about a day ago.  However: during testing, a major regression was discovered, reported on the issue tracker as #25027:
Python 3.5 includes some big changes on how Python is built on Windows.  One of those changes resulted in Python processes on Windows exceeding the maximum number of loadable shared libraries.  As a result Windows builds of Python could no longer run major Python software stacks like Pandas and Jupyter.  Fixing this required non-trivial last-minute changes to the Windows build--and those changes need testing.  We therefore elected to insert an extra release candidate before the final release, to get these changes into your hands as soon as possible, so that Windows users could test these changes.

As with all other Python 3.5 releases to date, this is a preview release, and its use is not recommended for production settings.  However, users are encouraged to test with Python 3.5.0rc4, especially Windows users who build or make use of numerous external packages.  (Non-Windows users will find little difference between Python 3.5.0rc3 and Python 3.5.0rc4.)

You can find Python 3.5.0rc4 here:


Windows and Mac users: please read the important platform-specific "Notes on this release" section near the end of that page.

Please kick the tires,


p.s.  Special thanks from the Python 3.5 release team to Christoph Gohlke for the bug report!