Updating pyVCP halpin from user defined M code Python file

#!/usr/bin/env python

# This file is M103 on the USER_M_PATH
# testing Python interface

import sys
import subprocess
import linuxcnc
import hal

print(sys.argv) #len always 3
        
try:
    s = linuxcnc.stat() # create a connection to the status channel
    s.poll() # get current values
except linuxcnc.error, detail:
    print "error", detail
    sys.exit(1)
	
g5x = (getattr(s, 'g5x_offset'))
rotation = (getattr(s, 'rotation_xy'))
print("g5x_offset = {}".format(g5x))
print("rotation = {}".format(rotation))

if False:
    # this is incorrect (error):
    hal.set_p("pyvcp.scope-xvalue", "888")

if True:
    # this works but is there a better/recommended method (not using subprocess)?
    subprocess.call("halcmd setp pyvcp.scope-xvalue 123", shell=True)

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import linuxcnc
c = linuxcnc.command()

c.mode(linuxcnc.MODE_MDI)
c.wait_complete()
 
c.mdi("M68 E0 Q123")

net vscope  pyvcp.scope-xvalue motion.analog-out-00

try:
    c.mode(linuxcnc.MODE_MDI)
except KeyboardInterrupt:
    pass