Create an API server quickly with Python + Falcon

I think you often use a web application framework to create an API server, but you don't need something so versatile, isn't it? This Falcon can be used in such a case. Falcon The minimum requirement is one file. Feel free to get started.

Installation

Use pip. Easy. If it doesn't work, try adding sudo.

$ pip install falcon

Try using

All you need is one file. Let's say sample.py.

Write resources

A resource is a class that handles requests. If you write ʻon_get or ʻon_post, it will handle the request of the corresponding method.

sample.py

...
class SampleResource:
    def on_get(self, req, resp):
        obj = {
            "header": "Hello!",
            "body": {
                "a": "hoge",
                "b": "fuga",
            }
        }
        resp.body = json.dumps(obj, ensure_ascii=False)
...

Write the routing

ʻAdd_route` connects the path with the class that handles the request.

sample.py

...
app = falcon.API()
app.add_route('/sample', SampleResource())
...

to start

Please change the address and port as appropriate. This part is not necessary when using gunicorn etc.

sample.py

...
if __name__ == "__main__":
    from wsgiref import simple_server

    httpd = simple_server.make_server("127.0.0.1", 8000, app)
    httpd.serve_forever()
...

test

It works normally with python.

$ python sample.py

When I try to access it, it seems to work. http://localhost:8000/sample

{"body": {"a": "hoge", "b": "fuga"}, "header": "Hello!"}

Use a little more

Use gunicorn

Install with pip.

$ pip install gunicorn

It seems to use 8000 ports by default.

$ gunicorn sample:app
[2016-12-15 20:37:20 +0900] [34136] [INFO] Starting gunicorn 19.6.0
[2016-12-15 20:37:20 +0900] [34136] [INFO] Listening at: http://127.0.0.1:8000 (34136)
...

Use -b to change the port (address).

$ gunicorn -b 127.0.0.1:8888 sample:app
[2016-12-15 20:41:29 +0900] [34225] [INFO] Starting gunicorn 19.6.0
[2016-12-15 20:41:29 +0900] [34225] [INFO] Listening at: http://127.0.0.1:8888 (34225)
...

Get request parameters

It is in the req in the arguments such as ʻon_get`.

sample.py

class ParamsResource:
    def on_get(self, req, resp):
        params = req.params
        resp.body = json.dumps(params, ensure_ascii=False)

app = falcon.API()
app.add_route('/params', ParamsResource())

/params => {} /params?a=hoge&b=fuga => {"a": "hoge", "b": "fuga"}

I got it. It's a good idea to read the request and response here. req/resp

Access the DB

There is no specific means in the standard. I will prepare it myself. I'm using MySQL in my environment, so I'll try to access it. First, install MySQL-Python. Introducing the familiar pip.

$ pip install MySQL-Python

And write. Please change the DB information as appropriate.

sample.py

...
class BusinnesTermResource:
    def on_get(self, req, resp):

        connection = MySQLdb.connect(
            host='localhost',
            port=3306,
            user='root',
            passwd='password',
            db='sample',
            charset='utf8',
            cursorclass=MySQLdb.cursors.DictCursor
        )
        cursor = connection.cursor()

        sql = "select * from business_term"
        cursor.execute(sql)
        term = cursor.fetchone()

        cursor.close()
        connection.close()

        resp.body = json.dumps(term, ensure_ascii=False)

app = falcon.API()
app.add_route('/businnes_term', BusinnesTermResource())
...

I got it.

{"term": "Hoge", "meening": "Fuga", "example": "sample", "id": 1}

Full code this time

sample.py

# -*- coding: utf-8 -*-
# sample.py
import falcon
import json
import MySQLdb
from MySQLdb.cursors import DictCursor

class BusinnesTermResource:
    def on_get(self, req, resp):

        connection = MySQLdb.connect(
            host='localhost',
            port=3306,
            user='root',
            passwd='password',
            db='sample',
            charset='utf8',
            cursorclass=MySQLdb.cursors.DictCursor
        )
        cursor = connection.cursor()

        sql = "select * from business_term"
        cursor.execute(sql)
        term = cursor.fetchone()

        cursor.close()
        connection.close()

        resp.body = json.dumps(term, ensure_ascii=False)

class SampleResource:
    def on_get(self, req, resp):
        obj = {
            "header": "Hello!",
            "body": {
                "a": "hoge",
                "b": "fuga",
            }
        }
        resp.body = json.dumps(obj, ensure_ascii=False)

class ParamsResource:
    def on_get(self, req, resp):
        params = req.params
        resp.body = json.dumps(params, ensure_ascii=False)

app = falcon.API()
app.add_route('/businnes_term', BusinnesTermResource())
app.add_route('/sample', SampleResource())
app.add_route('/params', ParamsResource())

if __name__ == "__main__":
    from wsgiref import simple_server

    httpd = simple_server.make_server("127.0.0.1", 8000, app)
    httpd.serve_forever()

in conclusion

It was very easy to make and it felt good. It's quick to write and start up, so it's crisp. I would like to use it for testing once, or with a suitable and good application that does not have such a large number of users.