Hi Fatemeh,
This is an error caused by the running of the python script. Have you edited the .py file in any way? And are you using the correct version of python to run the script? Some differences between Python 2.7 and Python 3 mean you have to match your call of python to the version the script was written in. I think I remember this happening to me and I think I edited the script to run using Python3.
Try running the script as:
python2.7 MmPbSaDecomp.py -bs -nbs 2000 -m contrib_MM.dat -p contrib_pol.dat -a sasa_contrib.dat
Does that work for you?
Natalie