tiangolo.fastapi/docs/tutorial/nosql-databases.md

FastAPI can also be integrated with any NoSQL.

Here we'll see an example using Couchbase, a document based NoSQL database.

You can adapt it to any other NoSQL database like:

• MongoDB
• Cassandra
• CouchDB
• ArangoDB
• ElasticSearch, etc.

Import Couchbase components

For now, don't pay attention to the rest, only the imports:

{!./tutorial/src/nosql-databases/tutorial001.py!}

Define a constant to use as a "document type"

We will use it later as a fixed field type in our documents.

This is not required by Couchbase, but is a good practice that will help you afterwards.

{!./tutorial/src/nosql-databases/tutorial001.py!}

Add a function to get a Bucket

In Couchbase, a bucket is a set of documents, that can be of different types.

They are generally all related to the same application.

The analogy in the relational database world would be a "database" (a specific database, not the database server).

The analogy in MongoDB would be a "collection".

In the code, a Bucket represents the main entrypoint of communication with the database.

This utility function will:

• Connect to a Couchbase cluster (that might be a single machine).
• Authenticate in the cluster.
• Get a Bucket instance.
• Return it.

{!./tutorial/src/nosql-databases/tutorial001.py!}

Create Pydantic models

As Couchbase "documents" are actually just "JSON objects", we can model them with Pydantic.

User model

First, let's create a User model:

{!./tutorial/src/nosql-databases/tutorial001.py!}

We will use this model in our path operation function, so, we don't include in it the hashed_password.

UserInDB model

Now, let's create a UserInDB model.

This will have the data that is actually stored in the database.

In Couchbase, each document has a document ID or "key".

But it is not part of the document itself.

It is stored as "metadata" of the document.

So, to be able to have that document ID as part of our model without it being part of the attributes (document contents), we can do a simple trick.

We can create an internal class, in this case named Meta, and declare the extra attribute(s) in that class.

This class doesn't have any special meaning and doesn't provide any special functionality other than not being directly an attribute of our main model:

{!./tutorial/src/nosql-databases/tutorial001.py!}

This Meta class won't be included when we generate a dict from our model, but we will be able to access it's data with something like:

my_user.Meta.key

!!! note Notice that we have a hashed_password and a type field that will be stored in the database.

But it is not part of the general `User` model (the one we will return in the path operation).

Get the user

Now create a function that will:

• Take a username.
• Generate a document ID from it.
• Get the document with that ID.
• Put the contents of the document in a UserInDB model.
• Add the extracted document key to our model.

By creating a function that is only dedicated to getting your user from a username (or any other parameter) independent of your path operation function, you can more easily re-use it in multiple parts and also add unit tests for it:

{!./tutorial/src/nosql-databases/tutorial001.py!}

f-strings

If you are not familiar with the f"userprofile::{username}", it is a Python "f-string".

Any variable that is put inside of {} in an f-string will be expanded / injected in the string.

dict unpacking

If you are not familiar with the UserInDB(**result.value), it is using dict "unpacking".

It will take the dict at result.value, and take each of its keys and values and pass them as key-values to UserInDB as keyword arguments.

So, if the dict contains:

{
    "username": "johndoe",
    "hashed_password": "some_hash",
}

It will be passed to UserInDB as:

UserInDB(username="johndoe", hashed_password="some_hash")

Create your FastAPI code

Create the FastAPI app

{!./tutorial/src/nosql-databases/tutorial001.py!}

Create the path operation function

As our code is calling Couchbase and we are not using the experimental Python await support, we should declare our function with normal def instead of async def.

Also, Couchbase recommends not using a single Bucket object in multiple "threads", so, we can get just get the bucket directly and pass it to our utility functions:

{!./tutorial/src/nosql-databases/tutorial001.py!}

Recap

You can integrate any third party NoSQL database, just using their standard packages.

The same applies to any other external tool, system or API.