About Systemd files

Embedded
1

Hi,
I am using Raspberry Pi 3 with Jessie. I want to start a service before network start attempt . I am using a gprs modem and it requires Power Up over Gpio. I have to power up modem before ppp0 attempt for connect.

Gprs powerup script

import time
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

GPIO.setup(12, GPIO.OUT)
GPIO.setup(13, GPIO.IN)
GPIO.setup(20, GPIO.OUT)


for i in range(0,20):
        GPIO.output(20, not GPIO.input(20))
        time.sleep(0.1)

if GPIO.input(13) == 1:
        print "gprs powerup"
        GPIO.output(12, 1)
        time.sleep(2)
        GPIO.output(12, 0)
        time.sleep(4)
else:
        print "gprs also powered"

Failed systemd file

[Unit]
Description=StartGprs
After: network-pre.target

[Service]
Type=idle
ExecStart=/usr/bin/python /home/pi/startGprs.py
StandardOutput=null

[Install]
WantedBy=network-pre.target
Alias=StartGprs.service