from mpi4py import MPI

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

send_data = f"Hello, from process {rank}!"
print(f"I am rank {rank}. I send to process {(rank+1)}")
print(f"I am rank {rank}. I receive from process {(rank-1)}")

if rank == size-1:
    comm.send(send_data, dest=(0))
else:
    comm.send(send_data, dest=(rank + 1))

recv_data = ""

if rank == 0:
    recv_data= comm.recv(source=(size - 1))
else:
    recv_data= comm.recv(source=(rank - 1))

print(f"I am rank {rank}. I have received: {recv_data}")