Tee and file redirections are very slow to write anything.

[Takashi Yano]

On Thu, 25 Feb 2021 09:51:48 +0000
"Henry S. Thompson wrote:
> Hamish McIntyre-Bhatty via Cygwin writes:
> 
> > I'm now thinking it may have been a Python script that was behaving this
> > way - I might go and double check in case this isn't what I think it is.
> 
> I have noticed recently (on a Linux box) that Python3.8 logging exhibits
> the problem you report, that is, no output until end of job.

stdbuf does not take effect for python, however, you can use
-u option or setting environment PYTHONUNBUFFERED=1.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>