From Fortran, I use
/dev/null on Linux/Mac/BSD/WSL/Cygwin and
NUL on Windows to get 10x faster speed on programs where output files are not wanted.
Too much disk writing from old Fortran code
Legacy Fortran code might dump data to disk, maybe lots of data that is slow and unused. Making slight changes to adapt these legacy Fortran programs to Python using f2py. I don’t want to hack around in the code commenting out or if’ing all those write statements. Thus I implement the null-writing behavior noted above.