import os
import subprocess

print "Before:", len(os.listdir("/proc/%d/fd" % os.getpid()))
p = subprocess.Popen("echo", stdout=subprocess.PIPE)
p.communicate()
print "After communicate:", len(os.listdir("/proc/%d/fd" % os.getpid()))
del p
print "After destruction:", len(os.listdir("/proc/%d/fd" % os.getpid()))