如何检查json列表中是否有属性？ 如果没有，我如何仅在缺少的地方添加它？

Question

I need to check if a .json file has a "quantity": float attribute in all of the lists and add that attribute to the places that doesn't have it alone but I don't know how to do it so (I have no experience with JSON format).

I have tried the .append and the .insert functions but none work like I need it to it.

I have a list like this:

{
    "id": 9746439,
    "name": "Home Theater LG com blu-ray 3D, 5.1 canais e 1000W",
    "quantity": 80,
    "price": 2199.0,
    "category": "Eletrônicos"
  },
  {
    "id": 2162952,
    "name": "Kit Gamer acer - Notebook + Headset + Mouse",
    "price": 25599.0,
    "category": "Eletrônicos"
  },

As you can see the second part doesn't have the "quantity" attribute and I need to add it like "quantity": 0 but have no idea how to do so. That occurs mutiple times in my list and I would like to know how I could write a code that would find those errors and add the attribute between "name" and "price" like the rest of the list.

Answer 1

jString = '''{
    "lst":[
    {
        "id": 9746439,
        "name": "Home Theater LG com blu-ray 3D, 5.1 canais e 1000W",
        "quantity": 80,
        "price": 2199.0,
        "category": "Eletrônicos"
     },
      {
        "id": 2162952,
        "name": "Kit Gamer acer - Notebook + Headset + Mouse",
        "price": 25599.0,
        "category": "Eletrônicos"
      }
    ]
    }'''
jObj = json.loads(jString)
for x in jObj["lst"]:
    if "quantity" not in x:
        x["quantity"] = 0

You can simply assign the attribute and safe it to a file or where ever you need it afterwards.

Answer 2

The easiest way is probably to load the json file into a Python data structure with json.load() , then insert the quantity item where it's missing, then write it to a new json file.

import json

# open the input file and load the contents into a python datastructure
with open('myfile.json') as input:
    data = json.load(input)

# iterate over each item
for item in data:
    # if "quantity" is not present, add it
    if 'quantity' not in item:
        item['quantity'] = 99.99

# write the updated data to a new file
with open('myfile_new.json', 'w') as output:
    json.dump(data, output)

Answer 3

I ran into the same conundrum the other day and solved it with the below code. I fully accept this is probably the "lazy" way to do it but it is super easy to read.

import json

json_string = '''{"results":[
{
    "id": 9746439,
    "name": "Home Theater LG com blu-ray 3D, 5.1 canais e 1000W",
    "quantity": 80,
    "price": 2199.0,
    "category": "Eletrônicos"
  },
  {
    "id": 2162952,
    "name": "Kit Gamer acer - Notebook + Headset + Mouse",
    "price": 25599.0,
    "category": "Eletrônicos"
  }]}'''

json_dict = json.loads(json_string)

for item in json_dict["results"]:
    try:
        item['quantity']
    except:
        item['quantity'] = 0

The approach I have gone for here is Try and Except, lets try and select the quantity key in your data and hey, if its not there lets just add it.

Let me know how you go with this approach.