Invalid command-line argument/ - partition / neb example

I used an input in neb example to do a test, running command is like this:

mpirun -np 3 lmp_mac_mpi -partition 3x1 -in in.neb.sivac.

It is totally fine. Lammps version is (March 2018). I modified it to calculate other material. It is still totally fine.
Then, I use a python code to call lammps, I have already tested Python/Lammps interface according to the manual (12.6) and it is fine. When I use this python code, running command is like this:

mpirun -np 3 python

there is an error: ERROR: Invalid command-line argument (…/lammps.cpp:252)

The important part of python code:
from lammps import lammps
lmp = lammps (name = “mac_mpi”, cmdargs = ["-partition 3x1"])

I also changed it to lmp = lammps (name = “mac_mpi”, cmdargs = ["-partition 1 1 1"]), it does not work.

I checked the manual and mail list. now I still could not find the solution.

I do not know if there is something wrong about lmp = lammps (name = “mac_mpi”, cmdargs = ["-partition 3x1"]).

Someone could help me? Try to solve it for a long time. Thanks

Department of Mechanical Engineering
University of Central Florida

You need to make that two arguments: - partition is one, and 3x1 is the other.

Thank you Axel! You are so helpful!