You need to pass two different arguments through RunProgram as a list, because you are actually passing two arguments to python. I do not have a mac, but on windows this python script:
import sys
print(sys.argv[1])
and this jsl script:
RunProgram(
executable("C:\path to\python.exe"),
options({"C:/path to/pythonscript.py", "hi"}),
readfunction("text")
);
returns:
"hi
"