youtube_subs.py

import requests

mickey_ch_id = 'UCyHQxCUs1ENbnj36FjesG7Q'
marc_ch_id = 'UCzhG6dIYhenVoRVgcdUexLQ'
stoyan_ch_id = 'stoyanjr'

base_url = 'https://www.googleapis.com/youtube/v3/'
path = 'subscriptions?part=id&channelId=UCyHQxCUs1ENbnj36FjesG7Q&fields=items%2Fid&key='

full_path = '{0}{1}{2}'.format(base_url, path, API_KEY) 

print full_path

r = requests.get(full_path)

print r.status_code

Expected output:

{
 "items": [
  {
   "id": "lna0AtDOcTuYBP1NtjnqcJKEqgcrmauOgEVCQiBuwm8"
  },
  {
   "id": "lna0AtDOcTuYBP1NtjnqcOJs9CVRSEmfMQb4Uzc3nu8"
  },
  {
   "id": "lna0AtDOcTuYBP1NtjnqcPok3RpREZzKMBHsaumrAE0"
  },
  {
   "id": "lna0AtDOcTuYBP1NtjnqcGCYZK-wOcNFREtqXmUh3Ws"
  },
  {
   "id": "lna0AtDOcTuYBP1NtjnqcEBkmlnRxiaVlqLAY3stiWM"
  }
 ]
}