Q:

Python: How to read stdout of subprocess in a nonblocking way

I am trying to make a simple python script that starts a subprocess and monitors its standard output.  Here is a snippet from the code:
process = subprocess. Popen([path_to_exe, os.path.join(temp_dir,temp_file)], stdout=subprocess. PIPE)
while True:   
    output=process.stdout.readline()
    print "test"

The problem is that the script hangs on output=process.stdout.readline() and that the line print "test" only executes after the subprocess is terminated. 
Is there a way to read standard output and print it without having to wait for the subprocess to terminate? 
The subprocess which I am starting is a Windows binary for which I do not have the source code. 
I have found several similar questions, but the answers are only applicable on Linux or in case I have the source of the suprocess I am starting. 

A:

Check select module
import subprocess
import select
import time
    
x=subprocess. Popen(['/bin/bash','-c',"while true; do sleep 5; echo yes; done"],stdout=subprocess. PIPE)
    
y=select.poll()
y.register(x.stdout,select. POLLIN)

while True:
  if y.poll(1):
     print x.stdout.readline()
  else:
     print "nothing here"
     time.sleep(1)

EDIT:
Threaded Solution for non posix systems:
import subprocess
from threading import Thread 
import time
 
linebuffer=[]
x=subprocess. Popen(['/bin/bash','-c',"while true; do sleep 5; echo yes; done"],stdout=subprocess. PIPE)

def reader(f,buffer):
   while True:
     line=f.readline()
     if line:
        buffer.append(line)
     else:
        break

t=Thread(target=reader,args=(x.stdout,linebuffer))
t.daemon=True
t.start()

while True:
  if linebuffer:
     print linebuffer.pop(0)
  else:
     print "nothing here"
     time.sleep(1)

