How can I print and display subprocess stdout and stderr output without distortion?

Question

Maybe there\'s someone out in the ether that can help me with this one. (I have seen a number of similar questions to this on SO, but none deal with both standard out and st

Answer 1

When I tested it, it seemed readline() is blocking. However I was able to access stdout and stderr separately using threads. Code sample as follows:

import os
import sys
import subprocess
import threading

class printstd(threading.Thread):
    def __init__(self, std, printstring):
        threading.Thread.__init__(self)
        self.std = std
        self.printstring = printstring
    def run(self):
        while True:
          line = self.std.readline()
          if line != '':
            print self.printstring, line.rstrip()
          else:
            break

pythonfile = os.path.join(os.getcwd(), 'mypythonfile.py')

process = subprocess.Popen([sys.executable,'-u',pythonfile], shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

print 'Process ID:', process.pid

thread1 = printstd(process.stdout, 'stdout:')
thread2 = printstd(process.stderr, 'stderr:')

thread1.start()
thread2.start()

threads = []

threads.append(thread1)
threads.append(thread2)

for t in threads:
    t.join()

However, I am not certain that this is thread-safe.