Reading from sys.stdin reads the whole file in

[Peter Otten]

Marko Rauhamaa wrote:

> Peter Otten <__peter__ at web.de>:
> 
>> In addition to what already has been said: you can switch off output
>> buffering of stdout/stderr with
>>
>> python -u out.py
>>
>> or by setting the PYTHONUNBUFFERED environment variable.
> 
> Very often such externalities are not in the control of the application
> developer.

Sometimes it's possible to use a wrapper script rather than to sprinkle your 
code with flush(). 

Sometimes the "offending" python script is not even written and maintained 
by you, and setting an environment variable may be a price you are willing 
to pay to keep it that way.