Find difference between two json files in python

Question

I have two json files as given below. And I want to find the difference between the two and write the differences to third json file. I am expecting json diff should be calculated- (B.json-A.json)

A.json

  [{
        "Number": 123,
        "brand": "Ford",
        "model": {
            "Mustang1": "2.64",
            "Mustang2": "3.00",
            "Mustang3": "1.00",
            "Mustang4": "1.64"
        }
    },
    {
        "Number": 321,
        "brand": "Toyota",
        "model": {
            "Camry": "2.64",
            "Prius": "3.00",
            "Corolla": "1.00",
            "Tundra": "1.64"
        }
    },
    {
        "Number": 111,
        "brand": "Honda",
        "model": {
            "Accord": "2.64",
            "Civic": "3.00",
            "Insight": "1.00",
            "Pilot": "1.64"
        }
    },
    {
        "Number": 891,
        "brand": "Ford",
        "model": {
            "Mustang1": "2.64",
            "Mustang8": "3.00",
            "Mustang3": "1.00",
            "Mustang6": "1.64"
        }
    },
    {
        "Number": 745,
        "brand": "Toyota",
        "model": {
            "Camry": "2.64",
            "Sienna": "3.00",
            "4Runner": "1.00",
            "Prius": "1.64"
        }
    },
    {
        "Number": 325,
        "brand": "Honda",
        "model": {
            "Accord": "2.64",
            "Passport": "3.00",
            "HR-V": "1.00",
            "Pilot": "1.64"
        }
    },
    {
        "Number": 745,
        "brand": "Accura",
        "model": {
            "TLX": "2.64",
            "MDX": "3.00"
        }
    },
    {
        "Number": 325,
        "brand": "Accura",
        "model": {
            "TLX": "2.64",
            "MDX": "3.00"
        }
    }
]

B.json

        [{
        "Number": 123,
        "brand": "Ford",
        "model": {
            "Mustang1": "2.64",
            "Mustang2": "3.00",
            "Mustang5": "1.64"
        }
    },
    {
        "Number": 321,
        "brand": "Toyota",
        "model": {
            "Camry": "2.64",
            "Prius1": "3.00",
            "Corolla1": "1.00",
            "Tundra": "1.64"
        }
    },
    {
        "Number": 111,
        "brand": "Honda",
        "model": {
            "Accord1": "2.64",
            "Civic1": "3.00",
            "Insight": "1.00",
            "Pilot": "1.64"
        }
    },
    {
        "Number": 891,
        "brand": "Ford",
        "model": {
            "Mustang1": "2.64",
            "Mustang8": "3.00",
            "Mustang3": "1.00",
            "Mustang6": "1.64"
        }
    },
    {
        "Number": 745,
        "brand": "Toyota",
        "model": {
            "Camry2": "2.64",
            "Sienna2": "3.00",
            "4Runner": "1.00",
            "Prius": "1.64"
        }
    },
    {
        "Number": 325,
        "brand": "Honda",
        "model": {
            "Accord": "2.64",
            "Passport2": "3.00",
            "HR-V2": "1.00",
            "Pilot": "1.64"
        }
    },
    {
        "Number": 745,
        "brand": "Accura",
        "model": {
            "TLX": "2.64",
            "MDX2": "3.00"
        }
    },
    {
        "Number": 325,
        "brand": "Accura",
        "model": {
            "TLX1": "2.64",
            "MDX": "3.00"
        }
    }
]

This prints:

{0: {'model': {'$delete': ['Mustang3', 'Mustang4'],
               'Mustang2': '1.00',
               'Mustang5': '1.64'}},
 1: {'model': {'$delete': ['Prius', 'Corolla'],
               'Corolla1': '1.00',
               'Prius1': '3.00'}},
 2: {'model': {'$delete': ['Accord', 'Civic'],
               'Accord1': '2.64',
               'Civic1': '3.00'}},
 4: {'model': {'$delete': ['Camry', 'Sienna'],
               'Camry2': '2.64',
               'Sienna2': '3.00'}},
 5: {'model': {'$delete': ['Passport', 'HR-V'],
               'HR-V2': '1.00',
               'Passport2': '3.00'}},
 6: {'model': {'$delete': ['MDX'], 'MDX2': '3.00'}},
 7: {'model': {'$delete': ['TLX'], 'TLX1': '2.64'}}}

Expected result: is calculated based on B.json-A.json. It will check what all keys were there in model in A.json but not present in B.json - grouped by other keys- Number, brand.

{"Number": 123, "brand": "Ford", 'model': {'Mustang2': '1.00', 'Mustang5': '1.64'}},
{"Number": 321, "brand": "Toyota", 'model': {'Corolla1': '1.00', 'Prius1': '3.00'}},
{"Number": 111, "brand": "Honda", 'model': {'Accord1': '2.64', 'Civic1': '3.00'}},
{"Number": 745, "brand": "Toyota", 'model': {'Camry2': '2.64', 'Sienna2': '3.00'}},
{"Number": 325, "brand": "Honda", 'model': {'HR-V2': '1.00', 'Passport2': '3.00'}},
{"Number": 745, "brand": "Accura", 'model': {'MDX2': '3.00'}},
{"Number": 325, "brand": "Accura", 'model': {'TLX1': '2.64'}}}

Both a_li and b_li contain the same json object! Perhaps you need to edit your question @user15051990 — Devesh Kumar Singh
– Devesh Kumar Singh, Commented May 6, 2019 at 13:59
yes looks like Mustang 2 was meant to be Mustang 3 in B.json — cardamom
– cardamom, Commented May 6, 2019 at 14:00

Lante Dellarovere · Accepted Answer · 2019-05-06 17:15:32Z

2

jsondiff doesn't do what you (probably) are trying to.
If A and B lists have not necessarily same Number and brand:

res = []
for b in B:
    r = dict(b)
    b_in_A = next((a for a in A if b["Number"] == a["Number"] and b["brand"] == a["brand"]), None)
    if b_in_A:
        r["model"] = {k: v for k, v in r["model"].items() if k not in b_in_A["model"]}
    res.append(r)
res

Output:

[{'Number': 123, 'brand': 'Ford', 'model': {'Mustang5': '1.64'}},
 {'Number': 321,
  'brand': 'Toyota',
  'model': {'Corolla1': '1.00', 'Prius1': '3.00'}},
 {'Number': 111,
  'brand': 'Honda',
  'model': {'Accord1': '2.64', 'Civic1': '3.00'}},
 {'Number': 891, 'brand': 'Ford', 'model': {}},
 {'Number': 745,
  'brand': 'Toyota',
  'model': {'Camry2': '2.64', 'Sienna2': '3.00'}},
 {'Number': 325,
  'brand': 'Honda',
  'model': {'HR-V2': '1.00', 'Passport2': '3.00'}},
 {'Number': 745, 'brand': 'Accura', 'model': {'MDX2': '3.00'}},
 {'Number': 325, 'brand': 'Accura', 'model': {'TLX1': '2.64'}}]

answered May 6, 2019 at 17:15

Lante Dellarovere

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8 Comments

user15051990 Over a year ago

I am getting error ` r = dict(b)` ValueError: dictionary update sequence element #0 has length 1; 2 is required. When I am running this code: A = open(path1) B = open(path2) res = [] for b in B: ` r = dict(b)` b_in_A = next((a for a in A if b["Number"] == a["Number"] and b["brand"] == a["brand"]), None)` if b_in_A: r["model"] = {k: v for k, v in r["model"].items() if k not in b_in_A["model"]} res.append(r)`

Lante Dellarovere Over a year ago

I can just guess. in my code A and B are lists of dictionaries, while your A and B are TextwIOWrapper (dict is parsing a string in your code). use import json module and do A = json.load(open(path1)) instead

user15051990 Over a year ago

I used A = json.load(open(path1)) And now I am getting json.decoder.JSONDecodeError: Extra data: line 2 column 1 (char 119)

Lante Dellarovere Over a year ago

this probably means your file is not a well formatted json. Post an example of your file

user15051990 Over a year ago

Updated, Checkout B.json.

|

Wes S. · Accepted Answer · 2019-05-06 14:06:32Z

0

jsondiff appears to just compare to individual json objects to find differences in their keys. You appear to be trying to just get a list of json objects not in both lists. This could just be done by looping through and checking to see if the object is in both lists:

unique_cars = [car for car in jf if car not in jg]
for car in jg:
    if car not in jf:
        unique_cars.append(car)

There's likely a stdlib that handles this sort of thing. But that's the logic you want.

answered May 6, 2019 at 14:06

Wes S.

514 bronze badges

1 Comment

user15051990 Over a year ago

I am trying to get keys present in B.json (model) but not in A.json. And this should be grouped with Number and brand.

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