Sort a JSON using Python

问题

I am trying ot sort a JSON Object using Python.

I have the following object :

{ 
  "text": "hello world",
  "predictions": 
   [
     {"class": "Class 1", "percentage": 4.63},
     {"class": "Class 2", "percentage": 74.68},
     {"class": "Class 3", "percentage": 9.38},
     {"class": "Class 4", "percentage": 5.78},
     {"class": "Class 5", "percentage": 5.53}
   ]
}

And I want to have this object instead :

{ 
  "text": "hello world",
  "predictions": 
   [
     {"class": "Class 2", "percentage": 74.68},
     {"class": "Class 3", "percentage": 9.38},
     {"class": "Class 4", "percentage": 5.78},
     {"class": "Class 5", "percentage": 5.53},
     {"class": "Class 1", "percentage": 4.63}
   ]
}

In fact, I want to order my array of objects by percentage.

I have tried this command :

sorted_obj = sorted(json_obj['predictions'], key=lambda k: k['percentage'], reverse=True)

And I had this error :

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: string indices must be integers

Any help is needed,

Thanks

回答1:

You can use sorted to sort the values, something like this :

json_obj = { 
  "text": "hello world",
  "predictions": 
   [
     {"class": "Class 1", "percentage": 4.63},
     {"class": "Class 2", "percentage": 74.68},
     {"class": "Class 3", "percentage": 9.38},
     {"class": "Class 4", "percentage": 5.78},
     {"class": "Class 5", "percentage": 5.53}
   ]
}

sorted_obj = dict(json_obj) 
sorted_obj['predictions'] = sorted(json_obj['predictions'], key=lambda x : x['percentage'], reverse=True)

print(sorted_obj)
print(json_obj)

This will result in :

# The sorted values based on 'predictions' -> 'percentage'
{'predictions': [{'percentage': 74.68, 'class': 'Class 2'}, {'percentage': 9.38, 'class': 'Class 3'}, {'percentage': 5.78, 'class': 'Class 4'}, {'percentage': 5.53, 'class': 'Class 5'}, {'percentage': 4.63, 'class': 'Class 1'}], 'text': 'hello world'}

# The original json_obj will remain unchanged as we have created a new object sorted_obj from values of json_obj using dict()
{'text': 'hello world', 'predictions': [{'class': 'Class 1', 'percentage': 4.63}, {'class': 'Class 2', 'percentage': 74.68}, {'class': 'Class 3', 'percentage': 9.38}, {'class': 'Class 4', 'percentage': 5.78}, {'class': 'Class 5', 'percentage': 5.53}]}

回答2:

You are almost right, you probably want to create a copy of the dictionary and then replace predictions's value to the sorted object. I'm assuming that you want to leave the original json_obj unchanged, hence the deepcopy (although it is unnecessary if we are simply doing a reassignment instead of in-place .sort).

>>> json_obj = { 
...   "text": "hello world",
...   "predictions": 
...    [
...      {"class": "Class 1", "percentage": 4.63},
...      {"class": "Class 2", "percentage": 74.68},
...      {"class": "Class 3", "percentage": 9.38},
...      {"class": "Class 4", "percentage": 5.78},
...      {"class": "Class 5", "percentage": 5.53}
...    ]
... }
>>> from copy import deepcopy
>>> sorted_json_obj = deepcopy(json_obj)
>>> sorted_json_obj['predictions'] = sorted(json_obj['predictions'], key=lambda k: k['percentage'], reverse=True)
>>> sorted_json_obj
{'predictions': [{'class': 'Class 2', 'percentage': 74.68},
                 {'class': 'Class 3', 'percentage': 9.38},
                 {'class': 'Class 4', 'percentage': 5.78},
                 {'class': 'Class 5', 'percentage': 5.53},
                 {'class': 'Class 1', 'percentage': 4.63}],
 'text': 'hello world'}

来源：https://stackoverflow.com/questions/43255909/sort-a-json-using-python

标签

python

json

sorting