Uninstalling 3.5 on Windows removes the py.exe launcher. If it was installed in the system-wide path (%SYSTEMROOT%), it may have replaced an existing copy from an earlier version. In this case, removing the launcher will break this remaining installation, requiring a repair.

Instead, the launcher should not be deleted. It uses the static CRT, hence has no DLL dependencies that would be removed by the uninstallation, and it will -- as PEP 397 demands -- select the Python version it starts based on the command line and the available installations.

Ceterum censeo: This bug could have been avoided by using MSI as the distribution package format and using the same component code for the launcher file in all supporting versions. Even if the file itself is different, the identical component code would have ensured through reference counting that it would only have been removed with the last referencing installation. Upward compatibility of older launchers could have become a problem, though.