"subprocess.Popen" - checking for success and errors

      output,error=pipe.communicate()

This will wait for command to finish and give you output or error depending on the state of command.

You can check return code of the process using check_call() method. In case if process returned non-zero value CalledProcessError will be raised.

Do you need to do anything with the output of the process?

The check_call method might be useful here. See the python docs here: https://docs.python.org/2/library/subprocess.html#subprocess.check_call

You can then use this as follows:

try:
  subprocess.check_call(command)
except subprocess.CalledProcessError:
  # There was an error - command exited with non-zero code

However, this relies on command returning an exit code of 0 for succesful completion and a non-zero value for an error.

If you need to capture the output as well, then the check_output method may be more appropriate. It is still possible to redirect the standard error if you need this as well.

try:
  proc = subprocess.check_output(command, stderr=subprocess.STDOUT)
  # do something with output
except subprocess.CalledProcessError:
  # There was an error - command exited with non-zero code

See the docs here: https://docs.python.org/2/library/subprocess.html#subprocess.check_output

Complete solution with check on return code, stdout and stderr:

import subprocess as sp

# ok
pipe = sp.Popen( 'ls /bin', shell=True, stdout=sp.PIPE, stderr=sp.PIPE )
# res = tuple (stdout, stderr)
res = pipe.communicate()
print("retcode =", pipe.returncode)
print("res =", res)
print("stderr =", res[1])
for line in res[0].decode(encoding='utf-8').split('\n'):
  print(line)

# with error
pipe = sp.Popen( 'ls /bing', shell=True, stdout=sp.PIPE, stderr=sp.PIPE )
res = pipe.communicate()
print("retcode =", pipe.returncode)
print("res =", res)
print("stderr =", res[1])

Prints:

retcode = 0
res = (b'bash\nbunzip2\nbusybox\nbzcat\n...zmore\nznew\n', b'')
stderr = b''
bash
bunzip2
busybox
bzcat
...
zmore
znew

retcode = 2
res = (b'', b"ls: cannot access '/bing': No such file or directory\n")
stderr = b"ls: cannot access '/bing': No such file or directory\n"