Problem recurrence

//install swig
sudo apt-get install swig
swig -c++ -python polyiou.i
python setup.py build_ext --inplace

//report error
ModuleNotFoundError: No module named '_polyiou'

Solution:

Swig is not installed correctly. Because there are python2 and python3 in the environment, the command to install swig is modified as follows

sudo apt-get install swig
swig -c++ -python polyiou.i
python3 setup.py build_ext --inplace