Let\'s say I insert the document.
post = { some dictionary }
mongo_id = mycollection.insert(post)
Now, let\'s say I want to add a field and
In pymongo you can update with:
mycollection.update({'_id':mongo_id}, {"$set": post}, upsert=False)
Upsert parameter will insert instead of updating if the post is not found in the database.
Documentation is available at mongodb site.
UPDATE For version > 3 use update_one instead of update:
mycollection.update_one({'_id':mongo_id}, {"$set": post}, upsert=False)