# This script can be used standalone
# So it doesn't depend on filesystem or Google Cloud for the credentials

from google.cloud import firestore
from google.oauth2 import service_account

key = 'your_credentials_json_string'

info = json.loads(key)
creds = service_account.Credentials.from_service_account_info(info)
db = firestore.Client(credentials=creds, project="project_name_goes_here")

# Upsert a document
doc_ref = db.collection(u'collection_name').document(u'document_id')
doc_ref.set({'attr': 'value'})

# Fetch all docs and print
collection_ref = db.collection(u'd')
docs = collection_ref.get()
for doc in docs:
    print(u'{} => {}'.format(doc.id, doc.to_dict()))

# AFAIK, Python lib doesn't support real-time listening for document updates