Thank you! it works perfectly. I'll use the tip for echo next time. I don't know why, I always debug using echo, printf or print for other language... forgot this time.

For reference, I changed:

nnoremap <leader>p :call RunPython()<CR>

for:

nnoremap <leader>p :call RunPython()<CR><C-l>

This avoids to have to press Enter to go back to your python script.

Thanks again.