don't understand popen2

[Martin P. Hellwig]

Hi all,

I was doing some popen2 tests so that I'm more comfortable using it.
I wrote a little python script to help me test that (testia.py):

---------------------------------
someline = raw_input("something:")

if someline == 'test':
     print("yup")
else:
     print("nope")
---------------------------------

And another little thing that does it's popen2 stuff:

---------------------------------
import popen2

std_out, std_in = popen2.popen2("testia.py")

x=std_out.readline()
print(x)

std_in.writelines("notgood")

x=std_out.readline()
print(x)
---------------------------------

Now what I expected was that I got the return one the first line: 
"something:" and on the second "nope", but instead of that I got:

 >>>
something:
Traceback (most recent call last):
   File "F:\coding\pwSync\popen_test\popen_test.py", line 8, in ?
     std_in.writelines("notgood")
IOError: [Errno 22] Invalid argument
 >>>

I played around a bit with flush, write and the order of first writing 
and then reading, the best I can get is no error but still not the 
expected output. I googled a bit copied some examples that also worked 
on my machine, reread the manual and the only conclusion I have is that 
I don't even understand what I'm doing wrong.

Would you please be so kind to explain my wrong doing?
(python 2.4 + win32 extensions on XPProSP2)

Thanks in advance!

-- 
mph