Zope 4 is the successor of Zope 2.13 supporting both Python 2.7 and Python 3. After the release of its final version 4.0:
- Zope 2.13 will drop into “security fixes only” mode. It will stay in this mode as long as there is a supported Plone version using Zope 2.13: The last Plone version using Zope 2.13 is Plone 5.1. Currently the last two major releases of Plone are officially supported. So with the final release of Plone 7 there will be no supported Plone version running on Zope 2.13. (Plone 5.2 will have a final release soon after the Zope 4 final release.)
- Zope 4 will only be a short-term supported release. It is an intermediate step to ease the transition to Python 3. There will be only a few bugfix releases until Zope 5 is ready. After 4.0.1 is released the work on Zope 5 will start.
- Zope 5 will only drop support for Python 2 and for APIs and imports which were already marked as deprecated in Zope 4 or even in Zope 2.13. So software which runs on Zope 4 using Python 3 without DeprecationWarnings should run fine on Zope 5, too. A first beta version of Zope 5 could be released by the end of 2019. With the final release of Zope 5, Zope 4 will drop into “security fixes only” mode.
If you have software running on Zope 2.13 with current Python 2.7, the migration plan looks like the following:
- Upgrade to Zope 4 on Python 2.7.
- Rollout your software on Zope 4 with Python 2.7 to prove your changes in a live environment.
- Upgrade the code of your software to Python 3.
- Migrate the ZODB to Python 3.
- Rollout your software using Zope 4 on Python 3 to prove it in a live environment.
- Drop the Python 2 support in your software.
- Upgrade to Zope 5 once it is released.
See the documentation how to install Zope. It also documents the migrations steps.