How return list on Python and Flask?

Question

I'm trying to return this list in flask. Teacher is a class and returns objects.

@app.route('/v1/teachers', methods=['GET'])
def getTeachers():
  teachers = []
  for teacher in Teacher.objects:
    teachers.append(teacher)
  return teachers

This code returns the typical error of TypeError: 'list' object is not callable The view function did not return a valid response.

I'm going crazy and I don't know what's going on. Does anyone know?

Thank you!!

EDIT:

I've already worked it out. The problem was not how to return the list, the problem was the serialization in JSON of the objects.

@app.route('/v1/teachers', methods=['GET'])
def getTeachers():
  teachers = []
  for teacher in Teacher.objects:
     teacherJson = teacher.to_json()
     teacherData = json.loads(teacherJson)
     teachers.append(teacherData)
  return jsonify({'teachers': teachers})

Thanks for your help.

Have you tried checking the value in `Teacher.objects` ? Also, you might need to return response in json. So, you will need to pass this list in json format. — Sumit S Chawla, Jan 02 '19 at 09:20
This doesn't work, it gives me back this error: `TypeError: is not JSON serializable` — laurajaime, Jan 02 '19 at 14:55

score 27 · Answer 1 · answered Jan 02 '19 at 09:25

27

You can't return a list directly from flask view.please try to jsonify

from flask import jsonify
@app.route('/v1/teachers', methods=['GET'])
def getTeachers():
   teachers = []
   for teacher in Teacher.objects:
      teachers.append(teacher)
   return jsonify(teachers)

answered Jan 02 '19 at 09:25

shijin

461
4
11

1

Does not work TypeError: Object of type List is not JSON serializable – ajbraus Oct 12 '19 at 05:53
This works at least for python 2. – kmui2 Mar 22 '20 at 17:27
@ajbraus take a look here https://stackoverflow.com/questions/16586180/typeerror-objectid-is-not-json-serializable – sid0972 Dec 29 '20 at 11:27

ybl · Answer 2 · 2022-09-02T07:31:26.497

4

You are returning a list, Flask expects a response to be returned.

from flask import jsonify

@app.route('/v1/teachers', methods=['GET'])
def getTeachers():
  teachers = []
  for teacher in Teacher.objects:
    teachers.append(teacher)
  return jsonify({"teachers": teachers})

edited Sep 02 '22 at 07:31

answered Jan 02 '19 at 09:27

ybl

1,510
10
16

1

This doesn't work, it gives me back this error: `TypeError: is not JSON serializable` – laurajaime Jan 02 '19 at 14:58
This does not work. – ajbraus Oct 12 '19 at 05:52
You can see the edit from OP in his answer. The `teacher` object has to be converted to JSON here if it's not automatically convertible. – ybl Oct 12 '19 at 05:59
`def test(): test = ['1','2','3'] return jsonify({'test':test})` – D.Snap Sep 01 '22 at 16:37

How return list on Python and Flask?

2 Answers2