How to use python to extract data that is pushed to stdout?

Question

I'm trying to do some scripting, but one of the utilities I have returns a value to stdout, where I would like to assign it to a variable.

The utility (candump) is constantly running and only prints to std out when it receives data.

import threading
from subprocess import call
import time

class ThreadClass(threading.Thread):
  def run(self):
    call(["candump","can0"])

t = ThreadClass()
t.start()
time.sleep(1)
call(["cansend", "can0", "-i", "0x601", "0x40", "0xF6", "0x60", "0x01", "0x00", "0x00", "0x00", "0x00"])

It returns the following values, which I would like to use in my python script:

<0x601> [8] 40 f6 60 01 00 00 00 00
<0x581> [8] 4b f6 60 01 96 08 00 00

The documentation on candump (what is dumping the data to stdout) is sparse

Is there I way I can tap into stdout and snatch the data going to it?

Sorry if this is incredibly obvious... learning Linux bit by bit.

Answer 1

If you aren't expecting a ton of output or don't mind reading it in all at once, you can use subprocess.check_output:

>>> import subprocess
>>> print subprocess.check_output(['ls', '/etc'])
adjtime
adobe
anacrontab
apparmor.d
arch-release
ati
at-spi2
avahi
axelrc
bash.bash_logout

If you do need to read it line-by-line, take a look at this question: read subprocess stdout line by line