Returning JSON Data

APIs most commonly return JSON.

Returning dicts (Flask 2+)

Flask can automatically serialize dicts:

from flask import Flask
 
app = Flask(__name__)
 
 
@app.route("/api/status")
def api_status():
    return {"status": "ok"}

from flask import Flask
 
app = Flask(__name__)
 
 
@app.route("/api/status")
def api_status():
    return {"status": "ok"}

jsonify()jsonify() gives you more control and is explicit:

from flask import Flask, jsonify
 
app = Flask(__name__)
 
 
@app.route("/api/user")
def api_user():
    return jsonify(id=1, name="Ravi")

from flask import Flask, jsonify
 
app = Flask(__name__)
 
 
@app.route("/api/user")
def api_user():
    return jsonify(id=1, name="Ravi")

Return a tuple to include a status code:

@app.route("/api/create", methods=["POST"])
def api_create():
    return {"created": True}, 201

@app.route("/api/create", methods=["POST"])
def api_create():
    return {"created": True}, 201

Returning objects that aren’t JSON-serializable (e.g., datetime)
- fix: convert to string or use a serializer
Doing return json.dumps(data)return json.dumps(data) without setting Content-Type: application/jsonContent-Type: application/json
- fix: use dict return or jsonifyjsonify