Getting Started With MongoDB and Sanic
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Sanic is a Python 3.6+ async web server and web framework that's written to go fast. The project's goal is to provide a simple way to get up and running a highly performant HTTP server that is easy to build, to expand, and ultimately to scale.
Unfortunately, because of its name and dubious choices in ASCII art, Sanic wasn't seen by some as a serious framework, but it has matured. It is worth considering if you need a fast, async, Python framework.
In this quick start, we will create a CRUD (Create, Read, Update, Delete) app showing how you can integrate MongoDB with your Sanic projects.
- Python 3.9.0
- A MongoDB Atlas cluster. Follow the "Get Started with Atlas" guide to create your account and MongoDB cluster. Keep a note of your username, password, and connection string as you will need those later.
1 git clone git@github.com:mongodb-developer/mongodb-with-sanic.git
You will need to install a few dependencies: Sanic, Motor, etc. I always recommend that you install all Python dependencies in a virtualenv for the project. Before running pip, ensure your virtualenv is active.
1 cd mongodb-with-sanic 2 pip install -r requirements.txt
It may take a few moments to download and install your dependencies. This is normal, especially if you have not installed a particular package before.
Once you have installed the dependencies, you need to create an environment variable for your MongoDB connection string.
1 export MONGODB_URL="mongodb+srv://<username>:<password>@<url>/<db>?retryWrites=true&w=majority"
Remember, anytime you start a new terminal session, you will need to set this environment variable again. I use direnv to make this process easier.
The final step is to start your Sanic server.
1 python app.py
Once the application has started, you can view it in your browser at http://127.0.0.1:8000/. There won't be much to see at the moment as you do not have any data! We'll look at each of the end-points a little later in the tutorial, but if you would like to create some data now to test, you need to send a
POST
request with a JSON body to the local URL.1 curl -X "POST" "http://localhost:8000/" \ 2 -H 'Accept: application/json' \ 3 -H 'Content-Type: application/json; charset=utf-8' \ 4 -d '{ 5 "name": "Jane Doe", 6 "email": "jdoe@example.com", 7 "gpa": "3.9" 8 }'
Try creating a few students via these
POST
requests, and then refresh your browser.All the code for the example application is within
app.py
. I'll break it down into sections and walk through what each is doing.We're going to use the sanic-motor package to wrap our motor client for ease of use. So, we need to provide a couple of settings when creating our Sanic app.
1 app = Sanic(__name__) 2 3 settings = dict( 4 MOTOR_URI=os.environ["MONGODB_URL"], 5 LOGO=None, 6 ) 7 app.config.update(settings) 8 9 BaseModel.init_app(app) 10 11 12 class Student(BaseModel): 13 __coll__ = "students"
Sanic-motor's models are unlikely to be very similar to any other database models you have used before. They do not describe the schema, for example. Instead, we only specify the collection name.
Our application has five routes:
- POST / - creates a new student.
- GET / - view a list of all students.
- GET /{id} - view a single student.
- PUT /{id} - update a student.
- DELETE /{id} - delete a student.
1 2 async def create_student(request): 3 student = request.json 4 student["_id"] = str(ObjectId()) 5 6 new_student = await Student.insert_one(student) 7 created_student = await Student.find_one( 8 {"_id": new_student.inserted_id}, as_raw=True 9 ) 10 11 return json_response(created_student)
Note how I am converting the
ObjectId
to a string before assigning it as the _id
. MongoDB stores data as BSON. However, we are encoding and decoding our data as JSON strings. BSON has support for additional non-JSON-native data types, including ObjectId
. JSON does not. Because of this, for simplicity, we convert ObjectIds to strings before storing them.The
create_student
route receives the new student data as a JSON string in a POST
request. Sanic will automatically convert this JSON string back into a Python dictionary which we can then pass to the sanic-motor wrapper.The
insert_one
method response includes the _id
of the newly created student. After we insert the student into our collection, we use the inserted_id
to find the correct document and return it in the json_response
.sanic-motor returns the relevant model objects from any
find
method, including find_one
. To override this behaviour, we specify as_raw=True
.The application has two read routes: one for viewing all students, and the other for viewing an individual student.
1 2 async def list_students(request): 3 students = await Student.find(as_raw=True) 4 return json_response(students.objects)
In our example code, we are not placing any limits on the number of students returned. In a real application, you should use sanic-motor's
page
and per_page
arguments to paginate the number of students returned.1 2 async def show_student(request, id): 3 if (student := await Student.find_one({"_id": id}, as_raw=True)) is not None: 4 return json_response(student) 5 6 raise NotFound(f"Student {id} not found")
The student detail route has a path parameter of
id
, which Sanic passes as an argument to the show_student
function. We use the id
to attempt to find the corresponding student in the database. The conditional in this section is using an assignment expression, a recent addition to Python (introduced in version 3.8) and often referred to by the incredibly cute sobriquet "walrus operator."If a document with the specified
id
does not exist, we raise a NotFound
exception which will respond to the request with a 404
response.1 2 async def update_student(request, id): 3 student = request.json 4 update_result = await Student.update_one({"_id": id}, {"$set": student}) 5 6 if update_result.modified_count == 1: 7 if ( 8 updated_student := await Student.find_one({"_id": id}, as_raw=True) 9 ) is not None: 10 return json_response(updated_student) 11 12 if ( 13 existing_student := await Student.find_one({"_id": id}, as_raw=True) 14 ) is not None: 15 return json_response(existing_student) 16 17 raise NotFound(f"Student {id} not found")
The
update_student
route is like a combination of the create_student
and the show_student
routes. It receives the id
of the document to update as well as the new data in the JSON body.We attempt to
$set
the new values in the correct document with update_one
, and then check to see if it correctly modified a single document. If it did, then we find that document that was just updated and return it.If the
modified_count
is not equal to one, we still check to see if there is a document matching the id
. A modified_count
of zero could mean that there is no document with that id
. It could also mean that the document does exist but it did not require updating as the current values are the same as those supplied in the PUT
request.It is only after that final
find
fail when we raise a 404
Not Found exception.1 2 async def delete_student(request, id): 3 delete_result = await Student.delete_one({"_id": id}) 4 5 if delete_result.deleted_count == 1: 6 return json_response({}, status=204) 7 8 raise NotFound(f"Student {id} not found")
Our final route is
delete_student
. Again, because this is acting upon a single document, we have to supply an id
in the URL. If we find a matching document and successfully delete it, then we return an HTTP status of 204
or "No Content." In this case, we do not return a document as we've already deleted it! However, if we cannot find a student with the specified id, then instead, we return a 404
.I hope you have found this introduction to Sanic with MongoDB useful. If you would like to find out more about Sanic, please see their documentation. Unfortunately, documentation for sanic-motor is entirely lacking at this time. But, it is a relatively thin wrapper around the MongoDB Motor driver—which is well documented—so do not let that discourage you.
To see how you can integrate MongoDB with other async frameworks, check out some of the other Python posts on the MongoDB developer portal.
If you have questions, please head to our developer community website where the MongoDB engineers and the MongoDB community will help you build your next big idea with MongoDB.
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