hello, >>>>> "Benyang" == Benyang Tang <btang at pacific.jpl.nasa.gov> writes: Benyang> How do I access stdin and stdout in python? os.popen Benyang> accepts either 'w' or 'r' mode, but not both at the same Benyang> time. you can use the popen2 module. -- erno PS. This is covered in the faq (http://www.python.org/doc/FAQ.html#4.30).