Documentation

The multiprocessing docs say:

Warning The 'spawn' and 'forkserver' start methods cannot currently be used with “frozen” executables (i.e., binaries produced by packages like PyInstaller and cx_Freeze) on Unix. The 'fork' start method does work.

But based on pyinstaller/pyinstaller#4865 (comment) and my own testing spawn works just fine (assuming you multiprocessing.freeze_support() as noted on the pyinstaller issue).