using subprocess.Popen does not suppress terminal window on Windows

[Steven]

I am calling a ruby program from a python gui and using
subprocess.Popen in Windows XP using python 2.6.  Unfortunately,
whenever the ruby program is called a blank command window appears on
screen, annoying my users.  Is there a way to suppress this behaviour?

Below is a minimal program that demonstrates the problem.  The problem
does not manifest if the python program is launched via the command
line.  To duplicate launch from Windows Explorer by double-clicking on
the python file.

--- call_double.pyw ---
from subprocess import *
import time

time.sleep(3) # to show that command window is result of call to Popen
p = Popen(['ruby.exe', 'double.rb'], stdin=PIPE, stdout=PIPE,
stderr=PIPE)
results = open('results.txt', 'w')
for n in range(10):
    p.stdin.write("%d\n" % n)
    result = p.stdout.readline().strip()
    results.write('double(%s) => %2s\n' % (n, result))
results.close()

--- end of call_double.pyw ---

--- double.rb ---
while true
    puts $stdin.gets().strip!.to_i * 2
    STDOUT.flush
end
--- end of double.rb ---

thanks for any help,
Steven Rumbalski