Return JSON response from Flask view

Question

I have a function that analyzes a CSV file with Pandas and produces a dict with summary information. I want to return the results as a response from a Flask view. How do I r

Answer 1

from flask import jsonify
app = Flask(__name__)
@app.route('/summary')
def summary():

   d = make_summary()
   return jsonify(d)

Answer 2

Flask 1.1.x

now Flask support request return with json directly, jsonify not required anymore

@app.route("/")
def index():
    return {
        "api_stuff": "values",
    }

is equivalent to

@app.route("/")
def index():
    return jsonify({
        "api_stuff": "values",
    })

for more information read here https://medium.com/octopus-wealth/returning-json-from-flask-cf4ce6fe9aeb and https://github.com/pallets/flask/pull/3111

Answer 3

Prior to Flask 0.11, jsonfiy would not allow returning an array directly. Instead, pass the list as a keyword argument.

@app.route('/get_records')
def get_records():
    results = [
        {
          "rec_create_date": "12 Jun 2016",
          "rec_dietary_info": "nothing",
          "rec_dob": "01 Apr 1988",
          "rec_first_name": "New",
          "rec_last_name": "Guy",
        },
        {
          "rec_create_date": "1 Apr 2016",
          "rec_dietary_info": "Nut allergy",
          "rec_dob": "01 Feb 1988",
          "rec_first_name": "Old",
          "rec_last_name": "Guy",
        },
    ]
    return jsonify(results=list)

Answer 4

""" Using Flask Class-base View """

from flask import Flask, request, jsonify

from flask.views import MethodView

app = Flask(**__name__**)

app.add_url_rule('/summary/', view_func=Summary.as_view('summary'))

class Summary(MethodView):

    def __init__(self):
        self.response = dict()

    def get(self):
        self.response['summary'] = make_summary()  # make_summary is a method to calculate the summary.
        return jsonify(self.response)

Answer 5

I use a decorator to return the result of jsonfiy. I think it is more readable when a view has multiple returns. This does not support returning a tuple like content, status, but I handle returning error statuses with app.errorhandler instead.

import functools
from flask import jsonify

def return_json(f):
    @functools.wraps(f)
    def inner(**kwargs):
        return jsonify(f(**kwargs))

    return inner

@app.route('/test/<arg>')
@return_json
def test(arg):
    if arg == 'list':
        return [1, 2, 3]
    elif arg == 'dict':
        return {'a': 1, 'b': 2}
    elif arg == 'bool':
        return True
    return 'none of them'

Answer 6

To return a JSON response and set a status code you can use make_response:

from flask import jsonify, make_response

@app.route('/summary')
def summary():
    d = make_summary()
    return make_response(jsonify(d), 200)

Inspiration taken from this comment in the Flask issue tracker.