Convert Pandas Dataframe to JSON format: how to group

Question

I have a Pandas Dataframe:

     nodes        x      y        z
0        1   0.0000  0.000   0.0000
1        2   0.0000  9.144   0.0000
2        3  19.5072  0.000   0.0000
3        4  19.5072  9.144   0.0000
4        5   9.7536  0.000   0.0000
..     ...      ...    ...      ...
175    176  19.5072  9.144  27.7368
176    177  19.5072  9.144  25.7556
177    178  19.5072  9.144  21.7932
178    179  19.5072  9.144  19.8120
179    180  19.5072  9.144  17.8308

to convert to JSON:

{
    "nodes": {
        "1": {
            "x": 0,
            "y": 0,
            "z": 0
        },
        "2": {
            "x": 0,
            "y": 9.144,
            "z": 0
        },
        "3": {
            "x": 19.5072,
            "y": 0,
            "z": 0
        },
        "4": {
            "x": 19.5072,
            "y": 9.144,
            "z": 0
        },
        "5": {
            "x": 9.7536,
            "y": 0,
            "z": 0
        },
    },
}

I just started to use python. After Google, I tried:

out = df.to_json(orient = 'records')
print(json.dumps(json.loads(out), indent=4))

It resulted in:

{
    "nodes": 1,
    "x": 0.0,
    "y": 0.0,
    "z": 0.0
},
{
    "nodes": 2,
    "x": 0.0,
    "y": 9.144,
    "z": 0.0
},
{
    "nodes": 3,
    "x": 19.5072,
    "y": 0.0,
    "z": 0.0
},

Please help. Thank you.

Answer 1

You can take advantage of the groupby function to achieve your desired output:

out = {'nodes': df.groupby('nodes').last().to_dict(orient='index')}
print(json.dumps(out, indent=4))

Results in:

{
    "nodes": {
        "1": {
            "x": 0.0,
            "y": 0.0,
            "z": 0.0
        },
        "2": {
            "x": 0.0,
            "y": 9.144,
            "z": 0.0
        },
        "3": {
            "x": 19.5072,
            "y": 0.0,
            "z": 0.0
        },
        "4": {
            "x": 19.5072,
            "y": 9.144,
            "z": 0.0
        },
        "5": {
            "x": 9.7536,
            "y": 0.0,
            "z": 0.0
        }
    }
}