The command mpirun can add command line arguments that are passed to your program. The MPICH (P4) version of mpirun does this. These extra command line arguments are used to help start the parallel job. When the command line is passed to MPI_Init the extra arguments are removed.
The point is that an application might not get the expected command line arguments. Accessing the command line arguments before and after MPI_init is called might not return the same thing.
As of version 1.1 the routine mpi.mpi_int will return the command line arguments after MPI_Init is called. Thus the perfered usage of this call is now
import sys sys.argv = mpi_init(len(sys.argv),sys.argv) |
After these calls sys.argv will contain the expected command line arguments