Adding a node into an xml tree

[snippsat]

My new concern now, is the way to have «/usr/lib/python3/dist-packages» in sys.path at Python's launch, without to have to

sys.path.append('/usr/lib/python3/dist-packages')

You shall never have to this,if so you have messes up installation.
I guess you have install Python 3.8 yourself?
I do recommend pyenv Simple Python Version Management.

So i see when you type python it start python 3.8.
When you try to install you see what happens because normal site-packages is not writeable
Then it tell that is satisfied in /usr/lib/python3/dist-packages this is default Python 3 installation and not 3.8.

remi@remi-Vostro-3550:~$ pip install beautifulsoup4
Defaulting to user installation because normal site-packages is not writeable
Requirement already satisfied: beautifulsoup4 in /usr/lib/python3/dist-packages (4.6.0)

Here some option to try

pip -V # Should point to Python 3.8,if not use pip3

python -m pip install beautifulsoup4

pip install --user beautifulsoup4

# Not recommend,but this is what many do unfortunately
sudo pip install beautifulsoup4

Now type python again and test if bs4 work in Python 3.8.