showing progress while spawning and running subprocess

I need to show some progress bar or something while spawning and running subprocess. How can I do that with python?

import subprocess

cmd = ['python','wait.py']
p = subprocess.Popen(cmd, bufsize=1024,stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr开发者_开发技巧=subprocess.PIPE)
p.stdin.close()
outputmessage = p.stdout.read() #This will print the standard output from the spawned process
message = p.stderr.read()

I could spawn subprocess with this code, but I need to print out something when each second is passing.

Since the subprocess call is blocking, one way to print something out while waiting would be to use multithreading. Here's an example using threading._Timer:

import threading
import subprocess

class RepeatingTimer(threading._Timer):
    def run(self):
        while True:
            self.finished.wait(self.interval)
            if self.finished.is_set():
                return
            else:
                self.function(*self.args, **self.kwargs)


def status():
    print "I'm alive"
timer = RepeatingTimer(1.0, status)
timer.daemon = True # Allows program to exit if only the thread is alive
timer.start()

proc = subprocess.Popen([ '/bin/sleep', "5" ])
proc.wait()

timer.cancel()

On an unrelated note, calling stdout.read() while using multiple pipes can lead to deadlock. The subprocess.communicate() function should be used instead.

As far as I see it all you need to do is put those reads in a loop with a delay and a print - does it have to be precisely a second or around about a second?