*The author selected the [Free and Open Source Fund](https://www.brightfunds.org/funds/foss-nonprofits) to receive a donation as part of the [Write for DOnations](https://do.co/w4do-cta) program.* ### Introduction [MongoDB](https://www.mongodb.com/) is a general-purpose, document-oriented, [NoSQL](https://www.digitalocean.com/community/tutorials/what-is-nosql) database program that uses [JSON](https://www.digitalocean.com/community/tutorials/an-introduction-to-json)-like documents to store data. Unlike tabular relations used in relational databases, JSON-like documents allow for flexible and dynamic schemas while maintaining simplicity. In general, NoSQL databases have the ability to scale horizontally, making them suitable for big data and real-time applications. A database driver or connector is a program that connects an application to a database program. To perform CRUD operations in MongoDB using Python, a driver is required to establish the communication channel. PyMongo is the recommended driver for working with MongoDB from Python. In this guide, you will write a Python script that creates, retrieves, updates, and deletes data in a locally installed MongoDB server on Ubuntu 20.04. In the end, you will acquire relevant skills to understand the underlying concepts in how data moves across MongoDB and a Python application. ## Prerequisites Before you move forward with this guide, you will need the following: - One Ubuntu 20.04 server with at least 1GB of RAM set up by following [the Ubuntu 20.04 initial server setup guide](https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-20-04), including a sudo non-root user and a firewall. - A Python 3 installation with an environment set up on Ubuntu 20.04 [using this quick start guide](https://www.digitalocean.com/community/tutorials/how-to-install-python-3-and-set-up-a-programming-environment-on-ubuntu-20-04-quickstart). - An installation of the latest MongoDB server compatible with Ubuntu 20.04 using the [How To install MongoDB on Ubuntu 20.04 guide](https://www.digitalocean.com/community/tutorials/how-to-install-mongodb-on-ubuntu-20-04). - A [security configuration of MongoDB on Ubuntu 20.04](https://www.digitalocean.com/community/tutorials/how-to-secure-mongodb-on-ubuntu-20-04) to prevent unauthorized access. ## Step 1 — Setting Up PyMongo In this step, you will install PyMongo, the recommended driver for MongoDB from Python. As a collection of tools for working with MongoDB, PyMongo facilitates database requests using syntax and an interface native to Python. To enable PyMongo, open your Ubuntu terminal and install from the [Python Package Index](https://pypi.org/). It is recommended to install PyMongo within a virtual environment in order to isolate your Python project. Refer to [this guide](https://www.digitalocean.com/community/tutorials/how-to-install-python-3-and-set-up-a-programming-environment-on-ubuntu-20-04-quickstart) if you missed how to set up a virtual environment in the prerequisites. ```command pip3 install pymongo ``` `pip3` refers to the Python 3 version of the popular [pip](https://pypi.org/project/pip/) package installer for Python. Note that within the Python 3 virtual environment you can use the command `pip` instead of `pip3`. Now, open the Python interpreter with the command below. The interpreter is a virtual machine that operates like a Unix shell, where you can execute Python code interactively. ```command python3 ``` You are in the interpreter when you get an output similar to what's below: ``` [secondary_label Output] Python 3.8.5 (default, Jan 27 2021, 15:41:15) [GCC 9.3.0] on linux Type "help", "copyright", "credits" or "license" for more information. ``` With a successful output, import `pymongo` in the Python interpreter: ```custom_prefix(>>>) import pymongo ``` Using the `import` statement, you can access the `pymongo` module and its code in your terminal. The `import` statement will run without raising exceptions. On the next line, import [getpass](https://docs.python.org/3/library/getpass.html): ```custom_prefix(>>>) from getpass import getpass ``` `getpass` is a module for managing password inputs. The module prompts you for a password without showing an input, and adds a security mechanism to prevent displaying passwords as plaintext. Here, make a connection with MongoClient to enable a MongoDB instance of your database. Declare a variable `client` to hold the MongoClient instance with `host`, `username`, `password`, and `authMechanism` as arguments: ```custom_prefix(>>>) client = pymongo.MongoClient('localhost', username='<^>username<^>', password=getpass('Password: '), authMechanism='SCRAM-SHA-256') ``` To connect to MongoDB with authorization enabled, MongoClient requires four arguments: - **host** - the hostname of the server on which MongoDB is installed. Since Mongo is local in this context, use `localhost`. - **username** and **password** - authorization credentials created after enabling authentication in MongoDB. - **authMechanism** - `SCRAM-SHA-256` is the default authentication mechanism supported by a cluster configured for authentication with MongoDB 4.0 or later. Once you've established the client connection, you can now interact with your MongoDB instance. ## Step 2 — Testing Databases and Collections In this step, you will get familiar with NoSQL concepts such as collections and documents as applied to MongoDB. MongoDB supports managing multiple independent databases within a MongoClient instance. You can access or create a database using attribute style on a MongoClient instance. Declare a variable `db` and assign the new database as an attribute of `client`: ```custom_prefix(>>>) db = client.<^>workplace<^> ``` In this context, the `workplace` database keeps track of employee records you will add such as the employee's name and role. Next, create a collection. Like tables in relational databases, collections store a group of documents in MongoDB. In your Python interpreter, create an `employees` collection as an attribute of `db` and assign it to a variable of the same name: ```custom_prefix(>>>) employees = db.<^>employees<^> ``` Create the `employees` collection as an attribute of `db` and assign it to a variable of the same name. <$>[note] **Note:** In MongoDB, databases, and collections are created lazily. This means that none of the above codes are actually executed until the first document is created. <$> Now that you've reviewed collections, let's look at how MongoDB represents documents, the basic structure for representing data. ## Step 3 — Performing CRUD Operations In this step, you will perform CRUD operations to manipulate data in MongoDB. Create, retrieve, update, and delete (CRUD) are the four basic operations in computer programming that one can perform to create persistent storage. To represent data in Python as JSON-like documents, dictionaries are used. Create a sample employee record with `name` and `role` attributes: ```custom_prefix(>>>) employee = { "name": "Sammy", "role": "Developer" } ``` As you can see, [Python dictionaries](https://www.digitalocean.com/community/tutorials/understanding-dictionaries-in-python-3) are very similar in syntax to JSON documents. PyMongo converts Python dictionaries to JSON documents for scalable data storage. At this point, insert the employee record into the `employees` collection: ```custom_prefix(>>>) employees.insert_one(employee) ``` Calling the `insert_one()` method on the `employees` collection, provide the employee record created earlier to be inserted. A successful insertion should return a successful output like below: ``` [secondary_label Output] ``` Now, verify you've successfully inserted the employee record and the collection. Make a query to find the employee you just created: ```custom_prefix(>>>) employees.find_one({"name": "Sammy"}) ``` Calling the` find_one()` method on the `employees` collection with a name query returns a single matching document. This method is useful when you have only one document, or when you are interested in the first match. The output should look similar to this: ``` [secondary_label Output] {'_id': ObjectId('606ae5b2358ddf640da46894'), 'name': 'Sammy', 'role': 'Developer'} ``` <$>[note] **Note:** When a document is inserted, a unique key `_id` is automatically added to the document if it does not already contain an `_id` key. <$> If the need arises to modify existing documents, use the `update_one()` method. The `update_one()` method requires two arguments, `query` and `update`: - **query** - `{"name": "Sammy"}` - PyMongo will use this query parameter to find documents with elements that match. - **update** - `{ "$set": {"role": "Technical Writer"} }` - The update parameter implements the [`$set operator`](https://docs.mongodb.com/manual/reference/operator/update/set/#mongodb-update-up.-set), which replaces the value of a field with the specified value. Call the `update_one()` method on the `employees` collection: ```custom_prefix(>>>) employees.update_one({"name": "Sammy"}, { "$set": {"role": "Technical Writer"} }) ``` A successful update will return an output similar to this: ``` [secondary_label Output] ``` To delete a single document, employ the `delete_one()` method. `delete_one()` requires a query parameter which specifies the document to delete. Execute the `delete_one()` method as an attribute of the `employees` collection with the name `Sammy` as a query parameter. ```custom_prefix(>>>) employees.delete_one({"name": "Sammy"}) ``` This will delete the only entry you have in your `employees` collection. ``` [secondary_label Output] ``` Using the `find_one()` method again, it is apparent that you've successfully deleted Sammy's employee record as nothing prints to the console. ```custom_prefix(>>>) employees.find_one({"name": "Sammy"}) ``` `insert_one()`, `find_one()`, `update_one()`, and `delete_one()` are great ways of getting started with performing CRUD operations in MongoDB with PyMongo. ## Conclusion In this guide, you have explored how to set up and configure PyMongo, the database driver, to connect Python code to MongoDB, as well as creating, retrieving, updating, and deleting documents. Although this guide focuses on introductory concepts, PyMongo offers more [powerful and flexible](https://pymongo.readthedocs.io/en/stable/tutorial.html) ways of working with MongoDB. For instance, you can make bulk inserts, query for more than one document, add indexes to queries, and many more. To learn more about MongoDB management, see [How To Back Up, Restore, and Migrate a MongoDB Database on Ubuntu 20.04](https://www.digitalocean.com/community/tutorials/how-to-back-up-restore-and-migrate-a-mongodb-database-on-ubuntu-20-04) and [How To Import and Export a MongoDB Database on Ubuntu 20.04](https://www.digitalocean.com/community/tutorials/how-to-import-and-export-a-mongodb-database-on-ubuntu-20-04).

How To Perform CRUD Operations in MongoDB Using PyMongo

Ubuntu

20.04

How To Perform CRUD Operations in MongoDB Using PyMongo on Ubuntu 20.04