Limitations

Import juliacall first from Python... sometimes

When using the omjlcomps Python library, it is sometimes necessary to import juliacall before other Python libraries (at least matplotlib, maybe others too) to avoid an error that looks like this:

$ cat test.py
import matplotlib
import juliacall
$ python test.py
ERROR: `ccall` requires the compilerTraceback (most recent call last):
  File "/home/dingraha/desk/pythoncall_wtf/test.py", line 2, in <module>
    import juliacall
  File "/home/dingraha/desk/pythoncall_wtf/venv-mybuild-with-libc-enable-shared-without-lto-without-optimizations-computed-gotos-no-dtrace-no-ssl/lib/python3.9/site-packages/juliacall/__init__.py", line 218, in <module>
    init()
  File "/home/dingraha/desk/pythoncall_wtf/venv-mybuild-with-libc-enable-shared-without-lto-without-optimizations-computed-gotos-no-dtrace-no-ssl/lib/python3.9/site-packages/juliacall/__init__.py", line 214, in init
    raise Exception('PythonCall.jl did not start properly')
Exception: PythonCall.jl did not start properly
$

This only occurs when using the system Python on certain Linux distributions (e.g., Python 3.9.7 on Red Hat Enterprise Linux 8.6). I've found three workarounds:

• import the juliacall module first in your run script, before anything else, or
• don't use the system Python: set up a Conda environment instead, or
• don't use RHEL (the system Python on e.g. Arch Linux doesn't appear to suffer from this bug).

See this PythonCall issue for a few more details.