How do I put a print statement in mrjob code for debugging purposes?

Question

How do I put a debug statement (like print) in reducer or mapper for mrjob. If I try to use print or sys.stderr.write(), I get an error TypeError: a bytes-like object is required, not 'str'

Answer 1

The error message indicates that the output handle is open to a binary stream, not a text stream (the difference between open(filename, 'w') and open(filename, 'wb'). Try

sys.stdout.write(message.encode())

If the encoding is not your default encoding, you have to add that explicitly (e.g. message.encoode('utf-8')).