Problem:
When trying to run a PySpice program, you see an error message such as
OSError: cannot load library 'libngspice.so': libngspice.so: cannot open shared object file: No such file or directory. Additionally, ctypes.util.find_library() did not manage to locate a library called 'libngspice.so'
Solution:
Install libngspice, often called libngspice0.
On Ubuntu, install it using
sudo apt -y install libngspice0-dev
You need to install the -dev library since libngspice0 only contains libngspice.so.0 whereas the -dev library contains libngspice.so which is required by pyspice.