Google URL-signing for Python3

gistfile1.py

from requests.packages.urllib3.util import parse_url
import hashlib
import hmac
import base64

""" Sign a URL using the client_secret """
__author__ = 'christopher@levire.com'

def sign_url(input_url=None, client_id=None, client_secret=None):
  """ Sign a request URL with a Crypto Key.

      Usage:
      from urlsigner import sign_url

      signed_url = sign_url(input_url=my_url,
                            client_id=CLIENT_ID,
                            client_secret=CLIENT_SECRET)

      Args:
      input_url - The URL to sign
      client_id - Your Client ID
      client_secret - Your Crypto Key

      Returns:
      The signed request URL
  """

  # Return if any parameters aren't given
  if not input_url or not client_id or not client_secret:
    return None

  # Add the Client ID to the URL
  input_url += "&client=%s" % (client_id)

  url = parse_url(input_url)

  # We only need to sign the path+query part of the string
  url_to_sign = url.path + "?" + url.query

  # Decode the private key into its binary format
  # We need to decode the URL-encoded private key
  decoded_key = base64.urlsafe_b64decode(client_secret)

  # Create a signature using the private key and the URL-encoded
  # string using HMAC SHA1. This signature will be binary.
  signature = hmac.new(decoded_key, url_to_sign.encode(), hashlib.sha1)

  # Encode the binary signature into base64 for use within a URL
  encoded_signature = base64.urlsafe_b64encode(signature.digest())

  original_url = url.scheme + "://" + url.netloc + url.path + "?" + url.query

  # Return signed URL
  return original_url + "&signature=" + encoded_signature.decode()

Transferred to python3 from:
https://developers.google.com/maps/documentation/business/webservices/auth