Arch Linux and Python

[waldeir]

In order to run the basic example in arch linux it is necessary do add the flag -lpython3.8. Assuming you are using bash, the command should be:
gfortran intro_to_forpy.F90 forpy_mod.o `python3-config --ldflags` -lpython3.8

[williamjameshandley]

Thank you very much for this hint @waldeir, you saved me a lot of time.

@ylikx this package is incredible.

[ylikx]

@waldeir thanks a lot for the info. I didn't try on Arch Linux, maybe python3-config --ldflags does not give the flags for the Python version that you want to use. Are you using Anaconda? Did you do conda activate?

@williamjameshandley Thank you very much!

[williamjameshandley]

Arch linux is a little bit idiosyncratic (and controversial) when it comes to its treatment of python, the main complication is that python means python3 rather than python2.

These commands on my arch linux system show the main problem:

$~ python --version
Python 3.8.2

$~ which python
/usr/bin/python

$~ which python-config
/usr/bin/python-config

$~ python-config --ldflags
 -L/usr/lib  -lcrypt -lpthread -ldl  -lutil -lm -lm

$~ ls /usr/lib/libpython*
/usr/lib/libpython2.7.so      /usr/lib/libpython3.5m.so.1.0  /usr/lib/libpython3.8.so
/usr/lib/libpython2.7.so.1.0  /usr/lib/libpython3.6m.so      /usr/lib/libpython3.8.so.1.0
/usr/lib/libpython3.5m.so     /usr/lib/libpython3.6m.so.1.0  /usr/lib/libpython3.so

which is that the python-config (and python3-config) don't actually point to a python library, and you need to point explicitly to libpython3.8, as there is no libpython at all.

@williamjameshandley Thank you very much!

I'm currently using this to call tensorflow from one of the cosmology standard fortran codes (CosmoMC).

[waldeir]

Thank you very much for this hint @waldeir, you saved me a lot of time.

@ylikx this package is incredible.

You are welcome!

[waldeir]

@waldeir thanks a lot for the info. I didn't try on Arch Linux, maybe python3-config --ldflags does not give the flags for the Python version that you want to use. Are you using Anaconda? Did you do conda activate?

@williamjameshandley Thank you very much!

No, i am not using anaconda. I am using the "python" (which provides python 3.8), python-matplotlib and python-numpy packages from the arch linux official repositories.

[ylikx]

@williamjameshandley @waldeir Thanks a lot for the clarification!

[ylikx]

Starting with Python 3.8 python3-config --ldflags does not output the -lpythonX.Y flag anymore. Use python3-config --ldflags --embed instead. (--embed is not available before Py 3.8). See issue #26