REMAP function doesn't work

I changed to
<return 0>

Nothing changed: " 'g886' is not a Python callable function.
May be it should be somehow compiled?

Probably too late now (I have a huge forum backlog)

You probably need to make the Python files executable.

And they might also need the magic incantation at the top.

Thank's for your unswer AndyPugh. No, it's not late for me. I simply shifted this problem because I didn't found any answer.

I tried as you said:
1) added line <#! usr/env python> (also tried <#!/usr/bin/env python>)
2) in terminal writed chmod +x <filename.py>
But it doesn't solve my problem.

This looks like a problem with toplevel.py and remap.py. Do those both exist?
LinuxCNC loads toplevel.py and then that imports remap.py which needs to either contain your "involute" function definition, or import a file that does.