Pyinstaller is used to turn python code into functional desktop applications. But there’s the common issue of it failing in virtual environments. Simply do:

pip install install

i.e. install the development version as specified in the documentation. If you simply do

pip install pyinstaller

in a virtual environment, you may encounter errors when attempting to use pyinstaller. If the error message includes something about matplotlib or another package not present in your virtual environment, this is an error characteristic to this particular issue.