Streaming stdin and stdout for subprocess progress reports

stream_subprocess_stdin_stdout.py

# If you don't need streaming stdout, just use communicate to access stdout and stderr instead
import threading
import subprocess
import sys
pr = subprocess.Popen(['command'], env=my_env, 
                        stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                        stderr=subprocess.STDOUT)
def pipe_writer():
    pr.stdin.write(input)
    pr.stdin.close()
thread = threading.Thread(target=pipe_writer)
thread.start()
while pr.poll() is None:
    l = pr.stdout.readline()
    sys.stdout.write(l)
    sys.stdout.flush()
thread.join() # This shouldn't be necessary, but just being safe.