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JSON MDODULE load loads dump dumps update and append
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‎contrib/advanced-python/index.md

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# List of sections
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- [Decorators/\*args/**kwargs](decorator-kwargs-args.md)
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- [JSON module](json-module.md)

‎contrib/advanced-python/json-module.md

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# JSON Module
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## What is JSON?
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- <a href="https://www.json.org/json-en.html">JSON (JavaScript Object Notation)</a> is a format for structuring data.
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- JSON is a lightweight, text-based data interchange format that is completely language-independent.
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- Similar to XML, JSON is a format for structuring data commonly used by web applications to communicate with each other.
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## Why JSON?
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- Whenever we declare a variable and assign a value to it, the variable itself doesn't hold the value. Instead, the variable holds an address in memory where the value is stored. For example:
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```python
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age = 21
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```
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- When we use `age`, it gets replaced with `21`. However, <i>age doesn't contain 21, it contains the address of the memory location where 21 is stored</i>.
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- While this works locally, transferring this data, such as through an API, poses a challenge. Sending your computer’s entire memory with the addresses is impractical and insecure. This is where JSON comes to the rescue.
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### Example JSON
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- JSON supports most widely used data types including String
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, Number, Boolean, Null, Array and Object.
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- Here is an example of JSON file
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```json
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{
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"name": "John Doe",
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"age": 21,
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"isStudent": true,
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"address": null,
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"courses": ["Math", "Science", "History"],
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"grades": {
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"Math": 95,
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"Science": 89,
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"History": 76
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}
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}
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```
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# Python JSON
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Python too supports JSON with a built-in package called `json`. This package provides all the necessary tools for working with JSON Objects including `parsing, serializing, deserializing, and many more`.
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## 1. Python parse JSON string.
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- To parse JSON string Python firstly we import the JSON module.
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- JSON string is converted to a Python object using `json.loads()` method of JSON module in Python.
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- Example Code:
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```python
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# Python program to convert JSON to Python
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import json
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# JSON string
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students ='{"id":"01", "name": "Yatharth", "department":"Computer Science Engineering"}'
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# Convert string to Python dict
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students_dict = json.loads(students)
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print(students_dict)
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print(students_dict['name'])
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```
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- Ouput:
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```json
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{'id': '01', 'name': 'Yatharth', 'department': 'Computer Science Engineering'}
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Yatharth
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```
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## 2. Python load JSON file.
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- JSON data can also be directly fetch from a json file
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- Example:
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```python
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import json
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# Opening JSON file
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f = open('input.json',)
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# Returns JSON object as a dictionary
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data = json.load(f)
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# Iterating through the json file
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for i in data['students']:
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print(i)
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# Closing file
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f.close()
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```
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- JSON file
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```json
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{
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"students":{
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{
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"id": "01",
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"name": "Yatharth",
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"department": "Computer Science Engineering"
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},
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{
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"id": "02",
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"name": "Raj",
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"department": "Mechanical Engineering"
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}
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}
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}
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```
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- Ouput
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```json
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{'id': '01', 'name': 'Yatharth', 'department': 'Computer Science Engineering'}
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{'id': '02', 'name': 'Raj', 'department': 'Mechanical Engineering'}
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```
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- `json.load()`: Reads JSON data from a file object and deserializes it into a Python object.
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- `json.loads()`: Deserializes JSON data from a string into a Python object.
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<hr>
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### Addtiotnal Context
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Relation between python data types and json data types is given in table below.
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</br>
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| Python Object | JSON Object |
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|-----------------|-------------|
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| Dict | object |
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| list, tuple | array |
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| str | string |
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| int, long, float | numbers |
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| True | true |
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| False | false |
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| None | null |
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## 3. Python Dictionary to JSON String
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- Parsing python dictionary to json string using `json.dumps()`.
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- Example Code:
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```python
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import json
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# Data to be written
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dictionary ={
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"id": "03",
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"name": "Suraj",
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"department": "Civil Engineering"
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}
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# Serializing json
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json_object = json.dumps(dictionary, indent = 4)
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print(json_object)
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```
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- Output:
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``` json
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{
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"department": "Civil Engineering",
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"id": "02",
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"name": "Suraj"
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}
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```
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## 4. Python Dictionary to JSON file.
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- - Parsing python dictionary to json string using `json.dump()`.
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- Example Code:
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``` python
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import json
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# Data to be written
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dictionary ={
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"name" : "Satyendra",
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"rollno" : 51,
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"cgpa" : 8.8,
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"phonenumber" : "123456789"
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}
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with open("sample.json", "w") as outfile:
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json.dump(dictionary, outfile)
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```
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- Ouput: `sample.json`
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``` json
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{
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"name" : "Satyendra",
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"rollno" : 51,
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"cgpa" : 8.8,
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"phonenumber" : "123456789"
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}
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```
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## 5. Append Python Dictionary to JSON String.
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- Append to an already existing string using `json.update()`.
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- Example :
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```python
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import json
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# JSON data:
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x = {
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"id": "03",
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"name": "Suraj"
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}
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# python object to be appended
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y = { "department": "Civil Engineering"}
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# parsing JSON string:
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z = json.loads(x)
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# appending the data
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z.update(y)
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# the result is a JSON string:
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print(json.dumps(z))
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```
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- Ouput:
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```json
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{"id": "03", "name": "Suraj", "department": "Civil Engineering"}
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```
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## 6. Append Python Dictionary to JSON File.
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- There is no direct function to append in file. So, we will load file in a dictionary, update dictionary then update content and convert back to json file format.
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- `data.json`
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``` json
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{
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"students":{
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{
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"id": "01",
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"name": "Yatharth",
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"department": "Computer Science Engineering"
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},
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{
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"id": "02",
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"name": "Raj",
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"department": "Mechanical Engineering"
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}
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}
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}
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```
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- Example Code:
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``` python
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import json
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# function to add to JSON
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def write_json(new_data, filename='data.json'):
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with open(filename,'r+') as file:
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# First we load existing data into a dict.
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file_data = json.load(file)
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# Join new_data with file_data inside students
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file_data["students"].append(new_data)
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# Sets file's current position at offset.
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file.seek(0)
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# convert back to json.
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json.dump(file_data, file, indent = 4)
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# python object to be appended
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y = {
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"id": "03",
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"name": "Suraj",
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"department": "Civil Engineering"
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}
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write_json(y)
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```
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- Output:
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```json
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{
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"students":{
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{
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"id": "01",
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"name": "Yatharth",
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"department": "Computer Science Engineering"
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},
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{
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"id": "02",
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"name": "Raj",
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"department": "Mechanical Engineering"
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},
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{
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"id": "03",
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"name": "Suraj",
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"department": "Civil Engineering"
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}
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}
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}
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```
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</br>
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<hr>
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The Python json module simplifies the handling of JSON data, offering a bridge between Python data structures and JSON representations, vital for data exchange and storage in modern applications.

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