Question 230404 in Json Question posted in
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How to edit or add a specific value to a JSON in Python

I have this function: def SetData(Username, Data):.

I have a JSON file called "data.json" and want to know the best way to make a value with the person’s "Username" and add the "Data" value to it. I also want to make sure that it will override any existing values with that username. Please note I have never coded with Python and this is my first project, so this is probably a really dumb question.

Thanks!

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2

Answers


  1. 0

    Your question isn’t dumb at all! Everyone starts somewhere, and I’m here to help. Let’s break down the problem and provide you with a step-by-step solution using Python.

    You want to create a function SetData(Username, Data) that updates a JSON file (data.json) with the provided Data for a given Username. Here’s how you can approach this:

    1. Load Existing Data: Read the contents of the JSON file into a Python data structure.
    2. Update Data: Update the data structure with the new Data value for the given Username.
    3. Write Data Back: Write the updated data structure back to the JSON file, effectively saving the changes.

    Here’s the code to accomplish this:

    import json

def SetData(Username, Data):
    # Step 1: Load Existing Data
    with open('data.json', 'r') as file:
        existing_data = json.load(file)
    
    # Step 2: Update Data
    existing_data[Username] = Data
    
    # Step 3: Write Data Back
    with open('data.json', 'w') as file:
        json.dump(existing_data, file, indent=4)  # indent for human-readable formatting

# Usage example
username = "example_user"
data_value = "new_data_value"
SetData(username, data_value)

    Please note:

    • Make sure you have the data.json file in the same directory as your Python script.
    • This code assumes that the JSON file initially contains a dictionary where the keys are usernames and values are associated data.
    • The function will update existing values or add new ones if the username doesn’t exist.

    Remember, when working with code and data, it’s always a good practice to make backups and test thoroughly.

    Updated for list type:

    If your data.json file is a list, and JSON file looks like this:

    [
    {
        "Username": "user1",
        "Data": "data1"
    },
    {
        "Username": "user2",
        "Data": "data2"
    },
    ...
]

    Here’s how you can modify the code:

    import json

def SetData(Username, Data):
    # Step 1: Load Existing Data
    with open('data.json', 'r') as file:
        existing_data = json.load(file)
    
    # Step 2: Find and Update Data
    for item in existing_data:
        if item["Username"] == Username:
            item["Data"] = Data
            break  # No need to continue searching if we found the username
    
    # Step 3: Write Data Back
    with open('data.json', 'w') as file:
        json.dump(existing_data, file, indent=4)  # indent for human-readable formatting

# Usage example
username = "example_user"
data_value = "new_data_value"
SetData(username, data_value)

    Please replace the JSON structure and the field names in the code with the actual structure of your data.json file. This code will search for the username in the list and update the associated data if the username is found. If not, you can decide whether you want to add a new entry or handle it differently.

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  2. 0

    First of all you need to decide on what the file structure is going to look like – i.e., is it a single JSON object or a list of objects. Then you need to consider what happens if the file doesn’t exist or has an incorrect structure – e.g., not valid JSON

    Let’s assume that you want your JSON file to contain a list of JSON objects then:

    import json
from pathlib import Path

FILENAME = Path('data.json')

def SetData(Username, Data):
    def _entry(username, data):
        return {
            'Username': username,
            'Data': data
        }
    try:
        mode = 'r+' if FILENAME.exists() else 'w'
        with open(FILENAME, mode) as f:
            jdata = [] if mode == 'w' else json.load(f)
            if isinstance(jdata, list):
                for e in jdata:
                    if e.get('Username') == Username:
                        e['Data'] = Data
                        break
                else:
                    jdata.append(_entry(Username, Data))
            else:
                jdata = _entry(Username, Data)
            f.seek(0)
            json.dump(jdata, f, indent=2)
            f.truncate()
    except Exception as e:
        print(e)
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