using subpocess for both reading and writing simultaneously

[dauriac]

Hello
I have a very simple python code cpt.py:

for i in xrange(2):
   print i                 # line 2
   ans = raw_input()       # line 3
   print ans               # line 4

I want to write another python program that run cpt.py,
read the first item (printed by line 2) echo that value
which will be read by line 3, read the new line (line 4)
an do it twice since cpt.py loop 2 times.

I tried without success (since I am asking !)

cmd = "cpt.py"
p = subprocess.Popen(cmd,stdout=subprocess.PIPE,stdin=subprocess.PIPE,stderr=subprocess.PIPE)
p.stdout.readline(ans) # read the print i (line 2)
p.stdin.writelines(ans)# write it (line3)
p.stdout.readline(ans) # read the print a (line 3)
p.stdout.readline(ans) # read  (line 2) second time
p.stdin.writelines(ans)# write it(line 3) second time
p.stdout.readline(ans) # read (ligne 3) second time

Thank you very much

JC