Parse Json file and save specific values

Question

I have this JSON file where the amount of id's sometimes changes (more id's will be added):

{
    "maps": [
        {
            "id": "blabla1",
            "iscategorical": "0"
        },
        {
            "id": "blabla2",
            "iscategorical": "0"
        },
        {
            "id": "blabla3",
            "iscategorical": "0"
        },
        {
            "id": "blabla4",
            "iscategorical": "0"
        }
    ]
}

I have this python code that has to print all the values of ids:

import json

data = json.load(open('data.json'))
variable1 = data["maps"][0]["id"]
print(variable1)
variable2 = data["maps"][1]["id"]
print(variable2)
variable3 = data["maps"][2]["id"]
print(variable3)
variable4 = data["maps"][3]["id"]
print(variable4)

I have to use variables, because i want to show the values in a dropdown menu. Is it possible to save the values of the id's in a more efficient way? How do you know the max amount of id's of this json file (in de example 4)?

Don't store them in variables, store them in a list. A list knows its length also. — Ilja Everilä, Feb 02 '18 at 11:23

magicleon94 · Answer 1 · 2018-02-02T11:39:30.533

You can get the number of id (which is the number of elements) by checking the length of data['maps']:

number_of_ids = len(data['maps'])

A clean way to get all the id values is storing them in a list.

You can achieve this in a pythonic way like this:

list_of_ids = [map['id'] for map in data['maps']]

Using this approach you don't even need to store the number of elements in the original json, because you iterate through all of them using a foreach approach, essentially.

If the pythonic approach troubles you, you can achieve the same thing with a classic foreach approach doing so:

list_of_ids = []
for map in data['maps']:
    list_of_ids.append(map['id'])

Or you can do with a classic for loop, and here is where you really need the length:

number_of_ids = len(data['maps'])
list_of_ids = []
for i in range(0,number_of_ids):
    list_of_ids.append(data['maps'][i]['id'])

This last is the classic way, but I suggest you to take the others approaches in order to leverage the advantages python offers to you!

You can find more on this stuff here!

Happy coding!

The poster is having trouble with the concept of a `for` loop. For now, suggesting list comprehensions to them is too much, in my opinion. — Adam Barnes, Feb 02 '18 at 11:35

Adam Barnes · Accepted Answer · 2018-02-02T11:27:37.623

1

data['maps'] is a simple list, so you can iterate over it as such:

for map in data['maps']:
    print(map['id'])

To store them in a variable, you'll need to output them to a list. Storing them each in a separate variable is not a good idea, because like you said, you don't have a way to know how many there are.

ids = []
for map in data['maps']:
    ids.append(map['id'])

edited Feb 02 '18 at 11:27

answered Feb 02 '18 at 11:21

Adam Barnes

2,922
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1

The OP also asked how many IDs were in the list. – Matt Morgan Feb 02 '18 at 11:22
Because of the dropdown menu I want to make, I have to store them in variables. Here I'm stuck. This example is a good way to start – Mvz Feb 02 '18 at 11:22
How are you creating the "dropdown"? I can't help more without seeing your code for that, or at least what framework. Please update your question. – Adam Barnes Feb 02 '18 at 11:28
I used a list for the dropdown. Thank you for changing the post with a list! OptionMenu(root, self.dropBoard, *ids).grid(row=0, column=0) – Mvz Feb 02 '18 at 11:33

Parse Json file and save specific values

2 Answers2