if STREAM.isatty():

[Hongyi Zhao]

On Fri, 30 Aug 2019 17:53:02 +1000, Chris Angelico wrote:

> That's because sys.stderr is never changing in your example here. Try
> checking whether sys.stdout is a TTY instead.

OMG, thanks a lot, this does the trick.

> 
> (Also, why the sleep? Seems unnecessary.)

Because without using sleep, the stuff on screen will display very 
shortly and then disappear.  Is this not your testing result?