Flask Working with JSON


Return a JSON Response from Flask API

Flask has a utility called jsonify() that makes it more convenient to return JSON responses

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/api/get-json')
def hello():
    return jsonify(hello='world') # Returns HTTP Response with {"hello": "world"}

Try it with curl

curl -X GET http://127.0.0.1:5000/api/get-json
{
  "hello": "world"
}

Other ways to use jsonify()

Using an existing dictionary:

person = {'name': 'Alice', 'birth-year': 1986}
return jsonify(person)

Using a list:

people = [{'name': 'Alice', 'birth-year': 1986},
          {'name': 'Bob', 'birth-year': 1985}]
return jsonify(people) 

Receiving JSON from an HTTP Request

If the mimetype of the HTTP request is application/json, calling request.get_json() will return the parsed JSON data (otherwise it returns None)

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/api/echo-json', methods=['GET', 'POST', 'DELETE', 'PUT'])                                                                                                    
def add():                                                                                                                              
    data = request.get_json()
    # ... do your business logic, and return some response
    # e.g. below we're just echo-ing back the received JSON data
    return jsonify(data)

Try it with curl

The parameter -H 'Content-Type: application/json' specifies that this is a JSON request:

 curl -X POST -H 'Content-Type: application/json' http://127.0.0.1:5000/api/echo-json -d '{"name": "Alice"}'               
{
  "name": "Alice"
}

To send requests using other HTTP methods, substitute curl -X POST with the desired method e.g. curl -X GET, curl -X PUT, etc.