How to generate a json file with a nested dictionary from pandas df?

I need to generate a json file with a specific format from a pandas dataframe. The dataframe looks like this:

And the json file needs to have the following format:

{
  "user_id": 1,
  "items": [{
        "product_id": 23,
        "date": 01-01-2022
        }, {
        "product_id": 24,
        "date": 05-01-2022
        }]
}
{
 "userid": 2,
 "items": [{
        "product_id": 56,
        "date": 05-06-2022
        }]
}
...etc

I’ve tried the following, but it’s not the right format:

result = (now.groupby('user_id')['product_id','date'].apply(lambda x: dict(x.values)).to_json())

Any help would be much appreciated!

>Solution :

out = (df[['product_id','date']].apply(dict, axis=1)
       .groupby(df['user_id']).apply(list)
       .to_frame('items').reset_index()
       .to_dict('records'))

print(out)

[{'user_id': 1, 'items': [{'product_id': 23, 'date': '01-01-2022'}, {'product_id': 24, 'date': '05-01-2022'}]},
{'user_id': 2, 'items': [{'product_id': 56, 'date': '05-06-2022'}]}, 
{'user_id': 3, 'items': [{'product_id': 23, 'date': '02-07-2022'}, {'product_id': 24, 'date': '01-02-2022'}, {'product_id': 56, 'date': '02-01-2022'}]}]