Partially update a JSON file in FastAPI

[innat]

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google "How to X in FastAPI" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
• I already checked if it is not related to FastAPI but to Swagger UI.
• I already checked if it is not related to FastAPI but to ReDoc.

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• I commit to help with one of those options 👆

Example Code

from fastapi import FastAPI
from fastapi.encoders import jsonable_encoder 
from pydantic import BaseModel 
app = FastAPI()

get_json_file = <read_from_disk> # no database 
root
 new_folder
   type: 'apple'
   format: 'png'
   count: 10
 old_folder
   type:
     sub_type: ['a', 'b', 'c']
     count: [2, 3, 4]
 upcoming_folder:
   type: '3D'
   format: ['.dicom', 'mha', 'nii']

@app.patch("/items/{item_id}", response_model=Item)
async def update_item(item_id: str, item: Item):
    # Read JSON file. And,
    # update specific value of it.
    # and return a updated json file. 

Description

I'm new to FastAPI. I've read the documentation, here, but couldn't resolve this. I also searched online, some SO question-answer were useful. But my requirements are too simple, there is no database to get.

The only thing I need to consider is to partially update some value of the JSON file (code above). Also, To get some values from the end-point, do I need to make an HTML page? From the end-point, can I pass multiple values to update this JSON file?

I mention my JSON file structure above. Now I can update some specific values of it. For example,

@app.patch("/items/{item_id}", response_model=Item)
   root['new_folder']['type'] = 'oragen' # replacing apple
   root['new_folder']['format'] = '.jpg'
   root[' upcoming_folder']['format'] = ['.dicom', 'nii', 'png']
   root[' upcoming_folder']['type'] = '2D'

Operating System

Windows

Operating System Details

No response

FastAPI Version

0.70.1

Python Version

3.9

Additional Context

No response

[YuriiMotov]

In general the approach is to use item.model_dump(exclude_unset=True), then iterate through keys and update values of JSON:

@app.patch("/items/{item_id}", response_model=Item)
async def update_item(item_id: str, item: Item):
    json_data = ... # Read JSON file.

    update_data = item.model_dump(exclude_unset=True)
    for key, value in update_data.items():
        json_data[key] = value

    return json_data # and return a updated json file.