Flask TypeError: argument of type 'NoneType' is not iterable - python-3.x

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');
}
})