When we want to use Unix command in python we can directly use os.system() to realize it. However, if we only want to return the output as a string, for example, return ls file names into a string, we need to use subprocess.check_out instead.

To note that, the output from subprocess.check_out() is a bytes object instead of a string, thus we need to further decode to transform into a string.

fileList = subprocess.check_output('ls someFolder/*', shell=True).decode('utf-8').strip().split('\n')

Source:
https://stackoverflow.com/questions/606191/convert-bytes-to-a-string