Flask TypeError: argument of type 'NoneType' is not iterable

Question

I am not sure why I am getting this TypeError:

File "C:/Users/PycharmProjects/REST/app.py", line 30, in valid_book_object if ("isbn" in book and "name" in book and "price" in book): TypeError: argument of type 'NoneType' is not iterable 127.0.0.1 - - [12/Nov/2018 14:22:29] "POST /books HTTP/1.1" 500 -

Code:

from flask import Flask, jsonify, request
from test import *
app=Flask(__name__)

books=[
    {'name': 'M',
     'price': 6.75,
    'isbn':123
    },
    {'name': 'G',
     'price': 7.75,
    'isbn':456
    },

]


#GET /store
@app.route('/books')  #first endpoint
def get_books():
    return jsonify({'books': books})

# POST /books
#{'name': 'F',
 #'price': 7.00,
 #'isbn': 789
 #},

def valid_book_object(book):
    if ("isbn" in book and "name" in book and "price" in book):
         return True
         print("true")
    else:
        return False
        print("false")


@app.route('/books', methods=['POST'])
def add_book():
    #return jsonify(request.get_json())
     request_data=request.get_json()
     if(valid_book_object(request_data)):
        books.insert(0, request_data)
        return "True"
     else:
        return "False"


#GET /books/456
@app.route('/books/<int:isbn>')  #second endpoint
def get_book_by_isbn(isbn):
    return_value={}
    for book in books:
        if book["isbn"]==isbn:
            return_value={
                'name': book["name"],
                'price':book["price"]
            }
    return jsonify(return_value)



app.run(port=5000)

Answer 1

You are not sending JSON data to /books route using POST method.

I tried your solution with postman and it worked. Also, if you want to use some route for GET and POST, don't split them. Use methods=['GET', 'POST']. Here is your code reformatted with PEP 8 standard:

from flask import Flask, jsonify, request

app = Flask(__name__)

books = [
    {'name': 'M',
     'price': 6.75,
     'isbn': 123
     },
    {'name': 'G',
     'price': 7.75,
     'isbn': 456
     }
]

# POST /books
# {
#     "name": "F",
#     "price": 7.00,
#     "isbn": 789
# }


def valid_book_object(book):
    if "isbn" in book and "name" in book and "price" in book:
        return True
    else:
        return False


@app.route('/books', methods=['GET', 'POST'])
def add_book():
    # If request is GET, just return JSON data of books.
    if request.method == 'GET':
        return jsonify({'books': books})
    else:
        # This is part if it is POST request
        request_data = request.get_json()
        if valid_book_object(request_data):
            books.insert(0, request_data)
            return "True"
        else:
            return "False"


# GET /books/456
@app.route('/books/<int:isbn>')  # second endpoint
def get_book_by_isbn(isbn):
    return_value = {}
    for book in books:
        if book["isbn"] == isbn:
            return_value = {
                'name': book["name"],
                'price': book["price"]
            }
            return jsonify(return_value)
    return 'No book with {} isbn value'.format(isbn)


if __name__ == '__main__':
    app.run(port=5000)

And here is the output from postman (you can see True at the bottom, that is what you return if POST was successful):

If you use postman, be sure to select application/json content-type.

If you are using JQuery ajax method, please read this answer. But anyway, here is using JQuery (tested):

data = JSON.stringify({
    name: "F",
    price: 7.00,
    isbn: 789
});
$.ajax({
  url: '/books',
  type: "POST",
  data: data,
  contentType: "application/json",
  dataType: "json",
  success: function(){
    console.log('Post executed successfully');
  }
})