How to fix PyVISA 'ValueError: Could not locate a VISA implementation. Install either the NI binary or pyvisa-py.'

Problem:

You are trying to use PyVISA to connect to an instrument, but you see an error message like

Traceback (most recent call last):
  File "TestPyVISA.py", line 3, in <module>
    rm = visa.ResourceManager()
  File "/usr/local/lib/python3.7/dist-packages/pyvisa/highlevel.py", line 1526, in __new__
    visa_library = open_visa_library(visa_library)
  File "/usr/local/lib/python3.7/dist-packages/pyvisa/highlevel.py", line 1493, in open_visa_library
    wrapper = _get_default_wrapper()
  File "/usr/local/lib/python3.7/dist-packages/pyvisa/highlevel.py", line 1470, in _get_default_wrapper
    raise ValueError('Could not locate a VISA implementation. Install either the NI binary or pyvisa-py.')
ValueError: Could not locate a VISA implementation. Install either the NI binary or pyvisa-py.

Solution:

Install the pyvisa-py Python package:

sudo pip3 install pyvisa-py

or, if you are still using Python 2.x:

sudo pip2 install pyvisa-py