A movie streaming service that does not let their users make comments on the movies they like. It's probably not a very good one, and there's a lot of improvement room for their user experience. Mflix is nothing like that, and it does allow you to provide feedback for future analysis and for us to do something more interesting with the service later on. Obviously, Mflix will be storing that information in MongoDB. And for that, we have a particular method I would like to be talk to you guys today about, which is this insert_one method here. It allows us to insert a documents into MongoDB collection, in particular to our comments collection. Now this is probably the simplest command that you can find in MongoDB but I still like to tell you all about it. So let's see this in action. And for that I'm going to use again, our Jupyter notebooks. There's one called insert-one for this lesson. And let's do the typical imports of importing everything that we need to use this particular notebook. We start by pymongo, pprint, and we're also going to import bson.objectid. And the built-in date time support of Python, which is datetime datetime. Now as usual we need to provide our MongoDB Atlas URI so we can connect to our instance. And it would be a nice idea for me to just print it out to see if we actually get a correct connection in place, so let's do just that. Once we run this you can see that the connection to the database is well executed, so we can move along. Now for inserting a single document we are just going to insert in this particular example, a dictionary. I'm going to create here, dictionary, then I'm going to call comment with some data on it. The data that we are storing in MongoDB is name, email, movie ID, text, and date, all of them of different data types. Name and email are the typical string data types. Movie_id will be a bson id, which I'm going to generate one right here, it's going to be fake a comment, so it's all good. Text, again, string, and then date, while we will be using datetime.utcnow. Another object I'm going to create here is this bypass validation flag that I'm going to put to false. Now the last thing that I need to do is call my mflix comments, insert_one method passing along my fake comments and this flag. Now why is this flag here and what is it's purpose? MongoDB allows us to define on a collection basis a validation of our documents. Obviously if we don't have one or if we just simply want to bypass it, MongoDB currently supports that in a very easy manner. We just need to pass the flag saying if we want to bypass evaluation or not. For this particular example I am going to do that just to show that we can. So if I do that, I get back an insert_one result that I'm storing in this variable here insert_results. Insert_result has two different fields as one field called acknowledged which will tell me if the command that I just emitted was acknowledged by the server. In this case, it's true, so we got there, we got to the server, fantastic. And now it also can tell me, if it's been acknowledged, what's the insert_id of our document, because we are not providing an _id field. And as you know, if we do not provide such _id field, MongoDB will create one for us, and there it is. But obviously we can, in fact, provide an _id, if we wish to do so. For example, here we are going to set our _id field to a string with the value some_id_field. If we do so, we can see that it is true, it has been acknowledged, and the inserted ID is the name or the string that we provided inside of the document, all checks correctly. And lastly, we need to also realize that a primary key cannot allow any duplicates. So if we try to insert the same document again or even just this different document with the same _id field, an error will be raised. MongoDB makes sure that if you tried to store two different documents with the same field value for _id, a DuplicateKeyError will be raised as you can find it here. And this is all on insert_one method.
