importing petsc4py fails in 22.04

[Christophe Prud'homme]

petsc4py cannot be used out of the box in python

install petsc4py
> apt install python3-petsc4py-real3.15 python3-petsc4py python3-petsc4py-real

then do
> python3 -c "import petsc4py"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'petsc4py'

to make it work you need to do :
> python3 -c "import sys;sys.path.append('/usr/lib/petscdir/petsc3.15/x86_64-linux-gnu-real/lib/python3/dist-packages'); import petsc4py"

then all good

an alternative is to install eg libpetsc64-real-dev
this will then configure the python path for petsc4py

[Christophe Prud'homme (prudhomm-debian)]

I am probably missing something here. I would be very happy to learn what.
I understand that we can switch between real/complex and 32/64 indexing but still there should be a way to configure alternatives at least no?

[Christophe Prud'homme (prudhomm-debian)]

None of the explanations to run petsc4py in /usr/share/doc/python3-petsc4py/README.Debian work by simply installing python3-petsc4py-real and python3-petsc4py

what works is to set by hand PETSC_DIR, there should be a default alternative, IMHO

> PETSC_DIR=/usr/lib/petscdir/petsc3.15/x86_64-linux-gnu-real python3 -c "import petsc4py; print(petsc4py.__path__)"
['/usr/lib/petscdir/petsc3.15/x86_64-linux-gnu-real/lib/python3/dist-packages/petsc4py']