I am building a simple function But I am stuck on an error, I am trying to sort json array based on datetime defined it the response. But JSON array also contains some None and Empty string dates like "". so It is showing

KeyError: 'date' when it sees None or empty date value

so I am trying to push these type of value in the last of the sorted json array which have None and empty string values (date).

example_response = [
    {
      "id": 2959,
      "original_language": "Permanent Job",
      "date": "2012-10-26",
      "absent": False
    },
    {
      "id": 8752,
      "original_language": "Intern Job",
      "date": "",
      "absent": True
    },
    {
      "adult": False,
      "id": 1300,
      "title": "Training Job",
      "date": "2020-07-25",
      "absent": False
    },
    {
      "adult": False,
      "id": 7807,
      "title": "Training Job",
      "absent": False
    },
]

program.py

def sorting_function(response):
    if response == True:
        sorted_data = sorted(example_response, key=lambda x: datetime.strptime(x['date'], "%Y-%m-%d"))
        print(sorted_data)

    return sorted_data

As you can see in example_response one dict has empty string and one don't have "date". When I run this function then it is showing KeyError: 'date'

What I have tried ?

I have also tried using

sorted_data = sorted(example_response, key=lambda x: (x['date'] is None, x['date'] == "", x['date'], datetime.strptime(x['date']), "%Y-%m-%d"))

But it still showing KeyError.

Any help would be much Appreciated.

CodePudding user response：

Dictionaries have a very useful get() function which you could utilise thus:

example_response = [
    {
      "id": 2959,
      "original_language": "Permanent Job",
      "date": "2012-10-26",
      "absent": False
    },
    {
      "id": 8752,
      "original_language": "Intern Job",
      "date": "",
      "absent": True
    },
    {
      "adult": False,
      "id": 1300,
      "title": "Training Job",
      "date": "2020-07-25",
      "absent": False
    },
    {
      "adult": False,
      "id": 7807,
      "title": "Training Job",
      "absent": False
    }
]

example_response.sort(key=lambda d: d.get('date', ''))

print(example_response)

In this case, missing or empty 'date' values would precede any other dates.

Output:

[{'id': 8752, 'original_language': 'Intern Job', 'date': '', 'absent': True}, {'adult': False, 'id': 7807, 'title': 'Training Job', 'absent': False}, {'id': 2959, 'original_language': 'Permanent Job', 'date': '2012-10-26', 'absent': False}, {'adult': False, 'id': 1300, 'title': 'Training Job', 'date': '2020-07-25', 'absent': False}]

CodePudding user response：

Don't call strptime if x['date'] is None

If the key is

lambda x: (x['date'] is None, datetime.strptime(x['date'], "%Y-%m-%d"))

Then the pair will be computed for all values, which means strptime will be called on all x['date'], including those that are None.

I suggest using a conditional, in order to only call strptime if x['date'] is not None:

lambda x: (0, datetime.strptime(x['date'], "%Y-%m-%d")) if x['date'] is not None else (1, 0)

Use x.get('date') instead of x['date'] if x might be missing the 'date' key

If x is a dict that doesn't have a 'date', then attempting to access x['date'] will always cause a KeyError, even for something as simple as x['date'] is None.

Instead, you can use dict.get, which doesn't cause errors. If a value is missing, dict.get will return None, or another value which you can provide as a second argument:

x = { "id": 2959, "original_language": "Permanent Job" }

print(x['date'])
# KeyError

print(x.get('date'))
# None

print(x.get('date', 42))
# 42

Finally, the key function for the sort becomes:

lambda x: (0, datetime.strptime(x.get('date'), "%Y-%m-%d")) if x.get('date') is not None else (1, 0)

Note that if the key function becomes too complex, it might be better to write it using def instead of lambda:

def key(x):
    date = x.get('date')
    if date is None:
        return (1, 0)
    else:
        return (0, datetime.strptime(date, "%Y-%m-%d"))