Question 295892 in Json Question posted in
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Remove from json if value of the key is null using python

I have a json file test.json,

{
    "person": [
        {
            "requestId": "0",
            "name": "ABC",
        "age" : 30,
            "city": ""
        }
    ]
}

Since city is null I dont want that in the json. so it should be like

{
    "person": [
        {
            "requestId": "0",
            "name": "ABC",
        "age" : 30,
            
        }
    ]
}

Also i wanted to update the same test.json file after removing null keys.

This is what I did and it did not remove the record.

    with open('test.json') as f:
        json_dict = json.load(f)
    for key in json_dict:
        if json_dict[key] is None:
            json_dict.pop(key)

Do I need to check value of the key separately?

Tags:

2

Answers


  1. 0

    I think there are a few problems in your initial approach:

    • You’re only iterating over the keys in the outermost dictionary. This outermost dictionary has one key: "person", which has a non-empty value. So that key is not being removed.
    • You’re trying to change the size of a dictionary while you loop over it. This is an error in Python.
    • You want to remove the key "city" which has a value of "", but you’re comparing "" to None.
    • You’re not writing the modified JSON object back to your file.

    Here’s some code that addresses these problems:

    import json

def recursively_remove_empty_keys(json_object):
    if isinstance(json_object, dict):
        keys_to_remove = []
        for key, value in json_object.items():
            if value == '':
                keys_to_remove.append(key)
            recursively_remove_empty_keys(value)
        for key in keys_to_remove:
            del json_object[key]
    elif isinstance(json_object, list):
        for elem in json_object:
            recursively_remove_empty_keys(elem)

def main():    
    filename = 'test.json'
    with open(filename) as f:
        json_object = json.load(f)

    recursively_remove_empty_keys(json_object)

    with open(filename, 'w') as f:
        json.dump(json_object, f, indent=4)

main()

    This code loads a JSON object, traverses the whole object, and deletes any dictionary keys whose values are the empty string.

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  2. 0

    As pointed out in the previous answer, there are 3 issues:

    1. nested dict in a list
    2. changing collections (lists or dicts) whilst looping is problematic.
    3. "" is none in json, but is it an empty string (string len = 0) in python.

    If you know the structure, then you can do this:

    d = {
    "person": [
        {
            "requestId": "0",
            "name": "ABC",
            "age" : 30,
            "city": ""
        }
    ]
}

# the bit you want to clean
json_dict:dict = d['person'][0]

# clean the inner dict
clean_dict = {}
for key in json_dict:
    if json_dict[key] != '':
        clean_dict[key] = json_dict[key]

d = {
    "person": [
        clean_dict
    ]
}

print(d)

    which will return this:

    {'person': 
    [
        {  
            'requestId': '0', 
            'name': 'ABC', 
            'age': 30
        }
    ]
}

    Alternatively, for a more general solution, you should use a recursive method that traverses the structure of the object.

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