Python subprocess readlines() hangs

Question

The task I try to accomplish is to stream a ruby file and print out the output. (NOTE: I don\'t want to print out everything at once)

Answer 1

Not sure what is wrong with your code, but the following seems to work for me:

#!/usr/bin/python

from subprocess import Popen, PIPE
import threading

p = Popen('ls', stdout=PIPE)

class ReaderThread(threading.Thread):

    def __init__(self, stream):
        threading.Thread.__init__(self)
        self.stream = stream

    def run(self):
        while True:
            line = self.stream.readline()
            if len(line) == 0:
                break
            print line,


reader = ReaderThread(p.stdout)
reader.start()

# Wait until subprocess is done
p.wait()

# Wait until we've processed all output
reader.join()

print "Done!"

Note that I don't have Ruby installed and hence cannot check with your actual problem. Works fine with ls, though.