python - prevent IOError: [Errno 5] Input/output error when running without stdout

Question

I have a script that runs automatically on server through cronjob and it import and run several other scripts.

Some of them use prints, which naturally creates

Answer 1

Modifying the builtin or changing sys.stdout should work (except for subprocesses—but you ruled those out) as long as you do it early enough. If not, though, there's a lower level trick that's much easier:

• run your python scripts with I/O redirection that discards output:

  python foo.py >/dev/null 2>&1
  

  (assuming Unix-y scripts, as implied by "cron" in the question)

• or, redirect file descriptors 1 and 2 (same idea as above, but done within your Python startup rather than as part of the cron-invoked command):

  import os
  fd = os.open(os.devnull, os.O_RDWR)
  # NB: even if stdin is closed, fd >= 0
  os.dup2(fd, 1)
  os.dup2(fd, 2)
  if fd > 2:
      os.close(fd)
  

  (this particular bit of code has the side effect of making /dev/null act as stdin, if all descriptors were closed). [Edit: I started with with open(...) and then switched to os.open and did not test the final version. Fixed now.]

All that said, a good cron really should have stdout and stderr connected somewhere, and should email the output/error-output to you. Not all cron versions are this nice though.