hello_p2p.py

from mpi4py import MPI

comm = MPI.COMM_WORLD
rank = comm.Get_rank()
size = comm.Get_size()

if rank == 0:
    for i in range(1, size):
        sendMsg = "Hello, Rank %d" %i
        comm.send(sendMsg, dest=i)

else:
    recvMsg = comm.recv(source=0)
    print(recvMsg)