Having trouble with tail -f standard input

[sab]

Hello,

I have been working on a python script to parse a continuously growing
log file on a UNIX server.  The input is the standard in, piped in
from the log file.  The application works well for the most part, but
the problem is when attempting to continuously pipe information into
the application via the tail -f command.  The command line looks
something like this:

tail -f <logfile> | grep <search string> | python parse.py

If I don't pipe the standard in to the python script, it displays any
new entries immediately on the screen.  However, if I pipe the
information into the script, the sys.stdin.readline() doesn't get any
new data until a buffer fills, after which it parses a block of new
information all at once (output is fine).  I need it to read the data
in real-time instead of waiting for the buffer to fill.  I have tried
running the script with the -u parameter but that doesn't seem to be
doing anything.  Also, if I run the program against a text file and
add a line to the text file (via cat >> <text file>) it picks it up
right away.  I'm sure that it's just a simple parameter that needs to
be passed or something along those lines but have been unable to find
the answer.  Any ideas would be appreciated.

Thanks!