[gentoo-user] ebuild : how to check for python version

[Helmut Jarausch]

Hi,
in an ebuild I have to apply a patch only if this package is installed  
for python3.9.
The ebuild should work for PYTHON_COMPAT=( python3_{8,9} )
How can I check for Pythons version in src_prepare or similar functions.

Many thanks for a hint,
Helmut