pymongo embedded document update

Question

I have following document in MongoDB 3.6

        forum_collection = { '_id' : id,
                         'tags': tags,
                         'sub_topic_name' : sub_topic_name,
                         'topic_creator' : creator_name,
                         'main_forum_name' : forum_name,
                         'threads' : [ {'thread_id' = uuid4,
                                        'thread_title = title,
                                        'thread_author = author,
                                        'thread_comment_cout = 0,
                                        'thread_body' = content,
                                        'thread_comments' = [ {'thread_comment_id' : uuid4,
                                                               'thread_comment_body': content,
                                                               'thread_commenter' : author,
                                                               'thread_comment_time'   : time
                                                               },
                                                            ]
                                        'thread_time' = time,
                                        },

                                     ],

SO I want to have forum_collection with multiple sub_topics, each sub_topics have threads and each thread have comments.

How can I add a new sub comment and update the thread_comment_count to 1 ? My following attempt fails miserably...my function passes three variables, sub_topic (to query the sub_topic_name), thread (to query thread_id) and thread_vals (to append new comment to thread_id)

forum_collection.find_one_and_update({'sub_topic_name': sub_topic, 'threads.thread_id' : thread},
                                     {'$inc': {'threads.'+thread+'.thread_comments_count': 1},
                                      '$addToSet': {thread + '.threads_comment': thread_vals}},
                                      return_document=pymongo.ReturnDocument.AFTER
                                     )

Answer 1

How does it fail? I don't know if it was a copy/paste error but your "thread_comment_ cout is misspelled . Also the $addToSet should refer to "threads" not "thread"

Answer 2

I needed to add $ at appropriate places....so not 'threads.'+thread+'.thread_comments_count' but 'threads.$.thread_comments_count'...

forum_collection.find_one_and_update({'sub_topic_name': sub_topic, 'threads.thread_id' : thread},
                                 {'$inc': {'threads.$.thread_comments_count': 1},
                                  '$addToSet': {'threads.$.thread_comments': thread_vals}},
                                  return_document=pymongo.ReturnDocument.AFTER
                                 )