Hello everybody. In this article, I'll talk about building simple asynchronous projects with the Sanic framework.
Introduction
Sanic is a very flask-like open-source Python web server and web framework with more than 10K stars that's written to go fast. It allows the usage of async/await
syntax added in Python 3.5 (read more), which makes your code non-blocking and speedy.
Sanic has pretty good documentation and it's maintained by the community, for the community.
The goal of the project is to provide a simple way to get a highly performant HTTP server up and running that is easy to build, to expand, and ultimately to scale.
Requirements
Before we start, let's install some packages and make sure that we have everything ready for the development of this project.
Note: Source code is available in my github.com repository. For each step, there is a corresponding commit.
Prerequisites:
Python3.6+
-
pipenv
(you can use any other package installer) -
PostgreSQL
(for database, can also be MySQL or SQLite)
Packages:
secure
is a lightweight package that adds optional security headers and cookie attributes for Python web frameworks.environs
is a Python library for parsing environment variables. It allows you to store configuration separate from your code, as per The Twelve-Factor App methodology.sanic-envconfig
is an extension that helps you bring command line & environment variables into your Sanic config.databases
is a Python package that allows you to make queries using the powerfulSQLAlchemy
Core expression language and provides support for PostgreSQL, MySQL, and SQLite.
Let's create an empty directory and initialize an empty Pipfile there.
pipenv -- python python3.6
Install all necessary packages using pipenv
commands below.
pipenv install sanic secure environs sanic-envconfig
For the database:
pipenv install databases[postgresql]
Choices are postgresql
, mysql
, sqlite
.
Structure
Now let's create some files and folders where we will write our actual code.
├── .env
├── Pipfile
├── Pipfile.lock
├── setup.py
└── project
├── __init__.py
├── __main__.py
├── main.py
├── middlewares.py
├── routes.py
├── settings.py
└── tables.py
We will use the setup.py
file to make the project folder available as a package in our code.
from setuptools import setup
setup(
name='project',
)
Installing…
pipenv install -e .
In the .env
file, we'll store some global variables like the database connection URL.
__main__.py
is created for making our project package executable from the command-line.
pipenv run python -m project
Initialization
Let's do our first call in __main__.py
file.
from project.main import init
init()
This is the beginning of our application. Now we need to create the init function inside of main.py
file.
from sanic import Sanic
app = Sanic(__name__)
def init():
app.run(host='0.0.0.0', port=8000, debug=True)
Simply creating the app from the Sanic class we can run it specifying host, port and optional debug keyword argument.
Running…
pipenv run python -m project
If you open http://0.0.0.0:8000 on your browser you'll see
Error: Requested URL / not found
We haven't created any routes yet, so it's fine for now. We will add some routes below.
Settings
Now we can modify the environment and settings. We need to specofy some variables in the .env
file, read them, and pass to Sanic app config.
.env
file.
DEBUG=True
HOST=0.0.0.0
POST=8000
Configuration…
from sanic import Sanic
from environs import Env
from project.settings import Settings
app = Sanic(__name__)
def init():
env = Env()
env.read_env()
app.config.from_object(Settings)
app.run(
host=app.config.HOST,
port=app.config.PORT,
debug=app.config.DEBUG,
auto_reload=app.config.DEBUG,
)
settings.py
file.
from sanic_envconfig import EnvConfig
class Settings(EnvConfig):
DEBUG: bool = True
HOST: str = '0.0.0.0'
PORT: int = 8000
Please note that I've added an optional auto_reload
argument which will activate or deactivate the Automatic Reloader.
Database
Now it's time to set up a database.
One little note about the databases package before we go ahead:
databases package uses
asyncpg
which is an asynchronous interface library for PostgreSQL. It's pretty fast. See results below.
We will use two of Sanic's listeners
where we will specify database connect and disconnect operations. Here are the listeners that we are going to use:
after_server_start
after_server_stop
main.py
file.
from sanic import Sanic
from databases import Database # <- this line
from environs import Env
from project.settings import Settings
app = Sanic(__name__)
def setup_database(): # <- this function
app.db = Database(app.config.DB_URL)
@app.listener('after_server_start')
async def connect_to_db(*args, **kwargs):
await app.db.connect()
@app.listener('after_server_stop')
async def disconnect_from_db(*args, **kwargs):
await app.db.disconnect()
def init():
env = Env()
env.read_env()
app.config.from_object(Settings)
setup_database() # <- this line
app.run(
host=app.config.HOST,
port=app.config.PORT,
debug=app.config.DEBUG,
auto_reload=app.config.DEBUG,
)
Once more thing. We need to specify DB_URL
in project settings and environment.
.env
file.
DEBUG=True
HOST=0.0.0.0
POST=8000
DB_URL=postgresql://postgres:postgres@localhost/postgres # <- this line
And in settings.py
file.
from sanic_envconfig import EnvConfig
class Settings(EnvConfig):
DEBUG: bool = True
HOST: str = '0.0.0.0'
PORT: int = 8000
DB_URL: str = '' # <- this line
Make sure that DB_URL
is correct and your database is running. Now you can access the database using app.db
. See more detailed information in the next section.
Tables
Now we have a connection to our database and we can try to do some SQL queries.
Let's declare a table in tables.py
file using SQLAlchemy.
import sqlalchemy
metadata = sqlalchemy.MetaData()
books = sqlalchemy.Table(
'books',
metadata,
sqlalchemy.Column('id', sqlalchemy.Integer, primary_key=True),
sqlalchemy.Column('title', sqlalchemy.String(length=100)),
sqlalchemy.Column('author', sqlalchemy.String(length=60)),
)
Here I assume that you already have a migrated database with a books table in it.
For creating database migrations, I recommend that you use Alembic
which is a lightweight and easy-to-use tool that you can use with the SQLAlchemy Database Toolkit for Python.
Now we can use any SQLAlchemy core queries. Check out some examples below.
# Executing many
query = books.insert()
values = [
{"title": "No Highway", "author": "Nevil Shute"},
{"title": "The Daffodil", "author": "SkyH. E. Bates"},
]
await app.db.execute_many(query, values)
# Fetching multiple rows
query = books.select()
rows = await app.db.fetch_all(query)
# Fetch single row
query = books.select()
row = await app.db.fetch_one(query)
Routes
Now we need to set up routes. Let's go to routes.py
and add a new route for books.
from sanic.response import json
from project.tables import books
def setup_routes(app):
@app.route("/books")
async def book_list(request):
query = books.select()
rows = await request.app.db.fetch_all(query)
return json({
'books': [{row['title']: row['author']} for row in rows]
})
Of course we need to call setup_routes
in init
to make it work.
from project.routes import setup_routes # <- this line
app = Sanic(__name__)
def init():
...
app.config.from_object(Settings)
setup_database()
setup_routes(app) # <- this line
...
Requesting…
$ curl localhost:8000/books
{"books":[{"No Highway":"Nevil Shute"},{"The Daffodil":"SkyH. E. Bates"}]}
Middlewares
What about checking the response headers and seeing what we can add or fix there?
$ curl -I localhost:8000
Connection: keep-alive
Keep-Alive: 5
Content-Length: 32
Content-Type: text/plain; charset=utf-8
As you can see we need some security improvements. There are some missing headers such as X-XSS-Protection
, Strict-Transport-Security
… so let's take care of them using a combination of middlewares
and secure packages.
middlewares.py
file.
from secure import SecureHeaders
secure_headers = SecureHeaders()
def setup_middlewares(app):
@app.middleware('response')
async def set_secure_headers(request, response):
secure_headers.sanic(response)
Setting up middlewares in main.py
file.
from project.middlewares import setup_middlewares
app = Sanic(__name__)
def init():
...
app.config.from_object(Settings)
setup_database()
setup_routes(app)
setup_middlewares(app) # <- this line
...
The result is:
$ curl -I localhost:8000/books
Connection: keep-alive
Keep-Alive: 5
Strict-Transport-Security: max-age=63072000; includeSubdomains
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Referrer-Policy: no-referrer, strict-origin-when-cross-origin
Pragma: no-cache
Expires: 0
Cache-control: no-cache, no-store, must-revalidate, max-age=0
Content-Length: 32
Content-Type: text/plain; charset=utf-8
Hope this small tutorial helped you to get started with Sanic. There are still many unexplored features in the Sanic framework that you can find and check out in the documentation.
Thanks for reading. Go Fast with Sanic and good luck!!!
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