matplotlib 3.0.0, cannot import name 'get_backend' from 'matplotlib'

Try this:

pip uninstall matplotlib
python -m pip install --upgrade pip
pip install matplotlib

Worked perfectly for me

This issue has been reported here and has been fixed here. The fix will be available in matplotlib 3.0.1, which is scheduled to be release within the next few days.

Until then you may either use python <= 3.6.6 with matplotlib 3.0.0. Or you may use matplotlib 2.2.3 or you may try the fix proposed in the linked issue, namely to create a matplotlibrc file in one of the paths where matplotlib would find it.