Adding an interesting subprocess demo and the poll method of a child process.

Author: Jonathan Rocher

ParallelComputing/demo_poll_subprocess.py

@@ -0,0 +1,20 @@
+""" Demo creating a subprocess and doing something in the master process when 
+the child is running. To know about the child's state we demo the poll method of 
+the process. 
+"""
+
+from subprocess import Popen
+import sys
+print "Starting..."
+# sleep for 10 seconds
+p = Popen(['sleep','10'])
+# continue on with processing
+print "Continuing",
+k=0
+while p.poll() is None:
+  k += 1 
+  if (k % 100000) == 0: 
+      print k//100000,
+      sys.stdout.flush()
+print
+print "Done", p.returncode