Python script for submitting Google Cloud Print jobs from macOS native print dialog using PDF Services.

gcp.py

#!/usr/local/bin/python3

# This script can be used to submit Google Cloud Print jobs from the PDF services menu in macOS
#
# Prerequisites:
# - Python 3.x
# - oauth2client installed
#
# Setup instructions:
# 1. Clone this gist into a directory called ".gcp" in your home directory. Assure
#    that "gcp.py" is executable.
# 2. Create a symbolic link to "gcp.py" in the "~/Library/PDF Services" directory. 
#    The name of this link will be displayed in the print dialog.
# 3. Create a set of app credentials in the Google developer console. Download the
#    credentials and store in "~/.gcp/client_secret.json".
# 4. Modify the value of the "PRINTER_ID" constant to be the UUID of the could printer
#    you want to submit jobs to.
#
# Usage:
# 1. Print using the system print dialog.
# 2. In the "PDF" drop down, select your custom service.
# 3. The default settings print one copy in black and white. To change the print settings,
#    modify "ticket.json". See documentation on the ticket format here:
#    https://developers.google.com/cloud-print/docs/cdd#cjt

import sys
import os
import logging
import time
import requests
import httplib2
from oauth2client.client import flow_from_clientsecrets
from oauth2client.file import Storage
from oauth2client.tools import run_flow

# constants
#PRINTER_ID = "__google__docs"                       # Save to Google Drive
PRINTER_ID = "f10fbf9c-0da8-6467-d9a4-861711e98e33"  # MatchBOX cloud print printer ID
GCP_HOME = os.environ["HOME"] + "/.gcp/"
CLIENT_SECRET_FILE = GCP_HOME + "client_secret.json"
SCOPE = "https://www.googleapis.com/auth/cloudprint"
STORAGE = Storage(GCP_HOME + "credentials.storage")
CLOUDPRINT_URL = "https://www.google.com/cloudprint/submit"

# set up logging
logging.basicConfig(filename=GCP_HOME + "gcp.log", level=logging.DEBUG, format="%(asctime)s - %(name)s - %(levelname)s - %(message)s")
logging.info("Starting print job...")

# check command line arguments
if len(sys.argv) != 4:
  logging.error("Incorrect number of arguments: %d", len(sys.argv))
  sys.exit(1)

title = sys.argv[1]
filename = sys.argv[3]
sys.argv = [sys.argv[0]]

# authorize with google
credentials = STORAGE.get()
if credentials is None or credentials.invalid:
  flow = flow_from_clientsecrets(CLIENT_SECRET_FILE, scope=SCOPE)
  http = httplib2.Http()
  credentials = run_flow(flow, STORAGE, http=http)

# build and submit print job
ticket = open(GCP_HOME + "ticket.json", "r")
body = {
  "printerid": PRINTER_ID,
  "title": [title],
  "ticket": ticket.read()
}
ticket.close()
files = {"content": open(filename,"rb")}
headers = {"Authorization":"Bearer "+str(credentials.get_access_token().access_token)}
r = requests.post(CLOUDPRINT_URL, data=body, files=files, headers=headers)
logging.debug(r.text)

# done
logging.info("Done.")

ticket.json

{
  "version": "1.0",
  "print": {
    "vendor_ticket_item": [],
    "color": {
      "type": "STANDARD_MONOCHROME"
    },
    "copies": {
      "copies": 1
    }
  }
}