How do I check if stdin has some data?

python redirect stdout stdin

mlzboy · Sep 21, 2010 · Viewed 50.7k times · Source

In Python, how do you check if sys.stdin has data or not?

I found that os.isatty(0) can not only check if stdin is connected to a TTY device, but also if there is data available.

But if someone uses code such as

sys.stdin = cStringIO.StringIO("ddd")

and after that uses os.isatty(0), it still returns True. What do I need to do to check if stdin has data?

Answer

On Unix systems you can do the following:

import sys
import select

if select.select([sys.stdin,],[],[],0.0)[0]:
    print "Have data!"
else:
    print "No data"

On Windows the select module may only be used with sockets though so you'd need to use an alternative mechanism.