A workaround from pyjulia might be to create a Julia function that can wrap a Julia Function around a Python function
fwrap = j.eval('f -> (args...) -> f(args...)') and then do j.dasslSolve(fwrap(f), 1.0, [0.0, 10.0]) Not super elegant, but occasionally inter-language calling requires this kind of "type massaging". (We occasionally have to do a similar thing in PyCall when passing Julia functions to Python, since some Python code only works with "native" Python functions.)