Python 3.6 to become the default target
On 2018-06-22, Python 3.6 will replace Python 3.5 in the default Python targets for Gentoo systems. The new default targets will be:
PYTHON_TARGETS="python2_7 python3_6" PYTHON_SINGLE_TARGET="python3_6"
If you have not overriden the value of those variables on your system, then your package manager will want to use the new targets immediately. In order to prevent dependency conflicts, please clean stray packages and rebuild/upgrade all packages with USE flag changes after the change, e.g.:
emerge --depclean emerge -1vUD @world emerge --depclean
Please note that upgrading dependencies in place may cause some of the package dependencies to be temporarily missing. While this should not affect scripts that are already fully loaded, it may cause ImportErrors while starting Python scripts or loading additional modules (only scripts running Python 3.5 are affected).
In order to improve stability of the upgrade, you may choose to temporarily enable both targets, i.e. set in /etc/portage/make.conf or its equivalent:
PYTHON_TARGETS="python2_7 python3_5 python3_6" PYTHON_SINGLE_TARGET="python3_5"
This will cause the dependencies to include both Python 3.5 and 3.6 support on the next system upgrade. Once all packages are updated, you can restart your scripts, remove the custom setting and run another upgrade to remove support for Python 3.5.
If you would like to postpone the switch to Python 3.6, you can copy the current value of PYTHON_TARGETS and/or PYTHON_SINGLE_TARGET to /etc/portage/make.conf or its equivalent:
PYTHON_TARGETS="python2_7 python3_5" PYTHON_SINGLE_TARGET="python3_5"
If you would like to migrate your systems earlier, you can do the same with the new value.
If you are still using Python 3.4, please consider switching to a newer version as it is reaching its end-of-life. The end-of-life dates for the currently used versions are:
Python 3.4 2019-03-16 Python 2.7 2020-01-01 Python 3.5 2020-09-13