python print statement issue when running with mpi

Question

I have a parallel python code (based on mpi4py) that I run with mpirun -n ....

I have a print statement in this code that conditionally uses end="\r" during the unrolling of the code, or end="\n" at the last step of the code (so I can keep the last version of the line before printing new stuff). This line is only printed by process 0.

So basically:

for i in range(N):
 
 < some stuff >
 
 if (mpi.rank == 0):
  if (i < N-1): end = "\r"
  else: end = "\n"
  print("things, more things", end=end)

• When running the code in sequential mode, everything works fine
• When running with mpi, the line only prints at the last step (so nothing shows on screen until the unrolling is done)
• If I replace "\r" with "\n" I get the expected behavior, i.e. all the lines print one after the other
• Adding sys.stdout.flush() does not help

Thanks in advance for your suggestions, I'm out of ideas.

python 3.8.9
mpi4py 3.1.6
openmpi 5.0.3