ModuleNotFoundError

When you start gnuradio-companion or execute grcc, if the system isn't configured properly for GRC to find the GNU Radio Python scripts and/or libraries, then you will see an error message similar to this one:

If you get this error message and you're running Linux, try the instructions on this page to see if any of them fix the issue. For issues and settings for OSX, see the MacInstall guide.

A. Determine the GNU Radio install prefix
If you don't know or remember your installation prefix, perform the following step: then use that prefix in place of  in the following commands.
 * on a terminal screen, enter

B. Finding the Python library
Using a terminal, enter the following command, substituting the prefix you found above in place of : find {your-prefix} -name gnuradio | grep "packages" Put the appropriate paths it found into the export commands below. Note that the paths are separated by colons

C. Setting PYTHONPATH
-  For almost all Debian / Ubuntu (and derivative) systems, and most other 32-bit Unix/Linux systems, the paths will look like this: export PYTHONPATH={your-prefix}/lib/{Py-version}/dist-packages:{your-prefix}/lib/{Py-version}/site-packages:$PYTHONPATH

-  For other 64-bit systems, the paths will look like this: export PYTHONPATH={your-prefix}/lib64/{Py-version}/site-packages:$PYTHONPATH

D. Setting LD_LIBRARY_PATH
-  For almost all Debian / Ubuntu (and derivative) systems, and most other 32-bit Unix/Linux systems, use: export LD_LIBRARY_PATH={your-prefix}/lib:$LD_LIBRARY_PATH

-  For other 64-bit systems, use: export LD_LIBRARY_PATH={your-prefix}/lib64:$LD_LIBRARY_PATH

E. Store the commands in a Bash start-up file
Once you have determined the correct two export commands to use, open your text editor and put them in your  or   or   file. Save the file. On your terminal enter. Then start a new terminal. As an example, your entries might be: export PYTHONPATH=/usr/local/lib/python3/dist-packages:/usr/local/lib/python3.6/dist-packages:$PYTHONPATH export LD_LIBRARY_PATH=/usr/local/lib:$LD_LIBRARY_PATH