[abuckenheimer]

> python3 -c 'while (1): print (1, end="")' | pv > /dev/null

python actually buffers its writes with print only flushing to stdout occasionally, you may want to try:

    python3 -c 'while (1): print (1, end="", flush=True)' | pv > /dev/null

which I find goes much slower (550Kib/s)