linux tee is not working with python?

Solution 1:

From man python:

   -u     Force stdin, stdout and stderr to  be  totally  unbuffered.   On  systems
          where it matters, also put stdin, stdout and stderr in binary mode.  Note
          that there is internal buffering in xreadlines(), readlines()  and  file-
          object  iterators  ("for  line  in sys.stdin") which is not influenced by
          this option.  To work around this, you will want to use  "sys.stdin.read‐
          line()" inside a "while 1:" loop.

So what you can do is:

/usr/bin/python -u client.py >> logfile 2>&1

Or using tee:

python -u client.py | tee logfile

Solution 2:

Instead of making it fully unbuffered you can make it linebuffered as it is normally with sys.stdout.reconfigure(line_buffering=True) (after import sys of course).

This was added in 3.7, docs: https://docs.python.org/3/library/io.html#io.TextIOWrapper.reconfigure