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Python Flask REST API Resourceful Blueprints Marshalling

Posted by William Ray Noble
William Ray Noble
22,190 Points

Empty Array or List

Hello, at around the 6-minute mark of the video, after he is done implementing marshal into the get method, Postman keeps returning an empty array or list. I've been over the code several times and can spot no discrepancies between Kenneth's and mine. Has Flask gone through an update that had rendered the code in the video in error? Thanks!

Megan Amendola
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Megan Amendola
Treehouse Teacher
Megan Amendola
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Megan Amendola
Treehouse Teacher

Hi! Flask has gone through a few updates since that course was created. If you post your code, it will be easier to see if there is in fact any difference or missing elements that might be throwing your code off.

1 Answer

Liliana Carnival
Liliana Carnival
39 Points
Liliana Carnival
Liliana Carnival
39 Points

Hello, I have the same issue. I use the same code in the workspace, the only exception is that I use flast_restful instead of flask.ext etc. from flask_restful import (Resource, Api, reqparse, inputs, url_for, fields, marshal, marshal_with)

The post gives me a 404 error, and the get does not give me what I expexct. I will really appreciate the help, thanks. Also, I dont know how to post code that well, but is really the same code as the last workspace, thanks!

from flask import jsonify, Blueprint, abort

from flask_restful import (Resource, Api, reqparse, url_for,
                           inputs, fields, marshal, marshal_with)

import models

course_fields = {
    'id': fields.Integer,
    'title': fields.String,
    'url': fields.String,
    'reviews': fields.List(fields.String)
}

def add_reviews(course):
    course.reviews = [url_for('resources.reviews.review', id=review.id)
                      for review in course.review_set]
    return course

def course_or_404(course_id):
    try:
        course = models.Course.get(models.Course.id==course_id)
    except models.Course.DoesNotExist:
        abort(404)
    else:
        return course

class CourseList(Resource):
    def __init__(self):
        self.reqparse = reqparse.RequestParser()
        self.reqparse.add_argument(
            'title',
            required=True,
            help='No course title provided',
            location=['form', 'json']
        )
        self.reqparse.add_argument(
            'url',
            required=True,
            help='No course URL provided',
            location=['form', 'json'],
            type=inputs.url
        )
        super().__init__()

    def get(self):
        courses = [marshal(add_reviews(course), course_fields)
                   for course in models.Course.select()]
        return {'courses': courses}

    @marshal_with(course_fields)
    def post(self):
        args = self.reqparse.parse_args()
        course = models.Course.create(**args)
        return (add_reviews(course), 201,
                {'Location': url_for('resources.courses.course', id=course.id)})

class Course(Resource):
    def __init__(self):
        self.reqparse = reqparse.RequestParser()
        self.reqparse.add_argument(
            'title',
            required=True,
            help='No course title provided',
            location=['form', 'json']
        )
        self.reqparse.add_argument(
            'url',
            required=True,
            help='No course URL provided',
            location=['form', 'json'],
            type=inputs.url
        )
        super().__init__()

    @marshal_with(course_fields)
    def get(self, id):
        return add_reviews(course_or_404(id))

    @marshal_with(course_fields)
    def put(self, id):
        args = self.reqparse.parse_args()
        course = course_or_404(id)
        query = course.update(**args)
        query.execute()
        course = course_or_404(id)
        return (course, 200,
                {'Location': url_for('resources.courses.course', id=id)})

    def delete(self, id):
        course = course_or_404(id)
        query = course.delete()
        query.execute()
        return '', 204, {'Location': url_for('resources.courses.courses')}

courses_api = Blueprint('resources.courses', __name__)
api = Api(courses_api)
api.add_resource(
    CourseList,
    '/api/v1/courses',
    endpoint='courses'
)
api.add_resource(
    Course,
    '/api/v1/courses/<int:id>',
    endpoint='course'
)

[Code markdown edited by staff] - Make sure to use backticks ` :)