Append item to MongoDB document array in PyMongo without re-insertion
You don't need to use to retrieve the document first just use the .update
method with the $push
operator.
def update_tags(ref, new_tag): coll.update({'ref': ref}, {'$push': {'tags': new_tag}})
Since update is deprecated you should use the find_one_and_update
or the update_one
method if you are using pymongo 2.9 or newer
Just to add to @ssytvane answer,and to answer @Guarav: you can add "upsert = True" if it does not exist:
def update_tags(ref, new_tag): coll.update({'ref': ref}, {'$push': {'tags': new_tag}}, upsert = True)
or
def update_tags(ref, new_tag): coll.update_one({'ref': ref}, {'$push': {'tags': new_tag}}, upsert = True)
You can simply do
1) If you want to append single entry
def update_tags(ref, new_tag): coll.update({'ref': ref}, {'$push': {'tags': new_tag}})
eg:
{ "_id" : ObjectId("561c199e038e42b10956e3fc"), "tags" : [ "tag1", "tag2", "tag3" ], "ref" : "4780"}>> update_tags("4780", "tag4"){'updatedExisting': True, u'nModified': 1, u'ok': 1, u'n': 1}>> coll.find_one({"ref":"4780"}){ "_id" : ObjectId("561c199e038e42b10956e3fc"), "tags" : [ "tag1", "tag2", "tag3" , "tag4" ], "ref" : "4780"}
2) If you want to append multiple entries
def update_tags(ref, new_tag): coll.update({'ref': ref}, {'$pushAll': {'tags': new_tag}}) #type of new_tag is list
eg:
{ "_id" : ObjectId("561c199e038e42b10956e3fc"), "tags" : [ "tag1", "tag2", "tag3" ], "ref" : "4780"}>> update_tags("4780", ["tag5", "tag6", "tag7"]){'updatedExisting': True, u'nModified': 1, u'ok': 1, u'n': 1}>> coll.find_one({"ref":"4780"}){ "_id" : ObjectId("561c199e038e42b10956e3fc"), "tags" : [ "tag1", "tag2", "tag3" , "tag4" , "tag5", "tag6", "tag7" ], "ref" : "4780"}
Note: If the key is not already present, then mongo will create new key.