Difference between subprocess Popen/call/check_output

Question

Hi everyone can anyone elaborate on the difference between

subprocess.Popen
subprocess.call
subprocess.check_output

and also if possible then please explain difference between x.readlines() versus x.communicate()?

i.e difference between

import subprocess
from subprocess import PIPE
ls = subprocess.Popen(['ls','-l'], stdout=subprocess.PIPE)
**out = ls.stdout.readlines()**
print out

and

import subprocess
from subprocess import PIPE
ls = subprocess.Popen(['ls','-l'], stdout=subprocess.PIPE)
out = ls.communicate()
print out

Answer 1

call and check_output (along with check_call) are just utility functions which call Popen under the hood.

• call returns the exit code of child process
• check_call raises CalledProcessError error if exit code was non zero
• check_output same as above but also returns output.

The difference between readlines and communicate is that readlines is simply a function made on the buffer (stdout) while communicate is a method of process class so it can handle different exceptions, you can pass input in it, and it waits for the process to finish.

Read more here