How to run freesurfer inside a python script

FSfromPython.py

import shlex
import subprocess
import sys
def which(program):
    def is_exe(fpath):
        return os.path.isfile(fpath) and os.access(fpath, os.X_OK)

    fpath, fname = os.path.split(program)
    if fpath:
        if is_exe(program):
            return program
    else:
        for path in os.environ["PATH"].split(os.pathsep):
            path = path.strip('"')
            exe_file = os.path.join(path, program)
            if is_exe(exe_file):
                return exe_file
        if is_exe(os.path.join(os.getenv('FREESURFER_HOME'),'bin',program)):
            return os.path.join(os.getenv('FREESURFER_HOME'),'bin',program)
        if is_exe(os.path.join('.',program)):
            return os.path.join('.',program)

    return None

def run_cmd(cmd,err_msg):
    """
    execute the comand
    """
    clist = cmd.split()
    progname=which(clist[0])
    if (progname) is None:
        print('ERROR: '+ clist[0] +' not found in path!')
        sys.exit(1)
    clist[0]=progname
    cmd = ' '.join(clist)
    print('#@# Command: ' + cmd+'\n')

    args = shlex.split(cmd)
    process = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    stdout, stderr = process.communicate()
    if stderr != b'':
        print('ERROR: '+ err_msg)

    return stdout

cmd = 'mri_seghead --invol ' + PATH_TO_IMAGE + ' --fill 255 --thresh 30 --nhitsmin 2 --dilate 5'
fs_output = run_cmd(cmd,"Failed to run mri_seghead")