Loop through JSON array for comparisons in python?

Question

is there a way to loop through two sets of JSON arrays and identify the additional array items from File 2 compared to File 1? Example below:

File 1:

{
    "Cars": [{
            "type": "Ford"
        },
        {
            "type": "BMW"
        }
    ]
}

File: 2

{
    "Cars": [{
            "type": "Ford"
        },
        {
            "type": "BMW"
        },
        {
            "type": "Vauxhall"
        },      
        {
            "type": "Fiat"
        }
    ]
}

Desired outcome:

The additons are:

{
        "Cars": [{
                "type": "Vauxhall"
            },      
            {
                "type": "Fiat"
            }
        ]
    }

I am struggling to get into the array in Python. Any help much appreciated.

user3483203 · Accepted Answer · 2018-03-14 19:18:57Z

1

If your data is this simple use in:

for c in y['Cars']:
  if c not in x['Cars']:
    print(c)

Or as a list comprehension:

diff_dict = {'Cars': [c for c in y['Cars'] if c not in x['Cars']]}

Output:

{'Cars': [{'type': 'Vauxhall'}, {'type': 'Fiat'}]}

You mentioned you were having a hard time getting the files into python. I used json.load()

edited Mar 14, 2018 at 19:18

answered Mar 14, 2018 at 19:11

user3483203

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1 Comment

Yuvraj Jaiswal Over a year ago

What if x array has the extra elements ? This will work only if he knows which one has extra elements.

Yuvraj Jaiswal · Accepted Answer · 2018-03-14 19:28:30Z

1

Not sure if this is the most optimal or the finest method, but it should work

Assuming you've arrays as dict in python

a = []
b = []
for val in array1["Cars"]:
    a.append(val["type"])
for val in array2["Cars"]:
    b.append(val["type"])
diff = ( set(a) | set(b) ) - ( set(a) & set(b) )

You can iterate over diff and create json/dict in required format.

edited Mar 14, 2018 at 19:28

answered Mar 14, 2018 at 19:10

Yuvraj Jaiswal

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