JSON MDODULE load loads dump dumps update and append

2024-05-18 13:18:25 +05:30 · 2024-05-18 13:18:25 +05:30 · 72909dc3ab
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 # List of sections

 - [Decorators/\*args/**kwargs](decorator-kwargs-args.md)
+- [JSON module](json-module.md)
--- a/contrib/advanced-python/json-module.md
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+# JSON Module
+
+## What is JSON?
+
+- <a href="https://www.json.org/json-en.html">JSON (JavaScript Object Notation)</a> is a format for structuring data.
+- JSON is a lightweight, text-based data interchange format that is completely language-independent.
+- Similar to XML, JSON is a format for structuring data commonly used by web applications to communicate with each other.
+
+## Why JSON?
+
+- 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:
+
+```python
+age = 21
+```
+
+- 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>.
+
+- 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.
+
+### Example JSON
+
+- JSON supports most widely used data types including String
+  , Number, Boolean, Null, Array and Object.
+- Here is an example of JSON file
+
+```json
+{
+  "name": "John Doe",
+  "age": 21,
+  "isStudent": true,
+  "address": null,
+  "courses": ["Math", "Science", "History"],
+  "grades": {
+    "Math": 95,
+    "Science": 89,
+    "History": 76
+  }
+}
+```
+
+# Python JSON
+
+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`.
+
+## 1. Python parse JSON string.
+
+- To parse JSON string Python firstly we import the JSON module.
+- JSON string is converted to a Python object using `json.loads()` method of JSON module in Python.
+- Example Code:
+
+```python
+# Python program to convert JSON to Python
+import json
+
+# JSON string
+students ='{"id":"01", "name": "Yatharth", "department":"Computer Science Engineering"}'
+
+# Convert string to Python dict
+students_dict = json.loads(students)
+print(students_dict)
+
+print(students_dict['name'])
+
+```
+
+- Ouput:
+
+```json
+{'id': '01', 'name': 'Yatharth', 'department': 'Computer Science Engineering'}
+Yatharth
+```
+
+## 2. Python load JSON file.
+
+- JSON data can also be directly fetch from a json file
+- Example:
+
+```python
+import json
+# Opening JSON file
+f = open('input.json',)
+
+# Returns JSON object as a dictionary
+data = json.load(f)
+
+# Iterating through the json file
+for i in data['students']:
+    print(i)
+
+# Closing file
+f.close()
+```
+
+- JSON file
+
+```json
+{
+  "students":{
+    {
+      "id": "01", 
+      "name": "Yatharth", 
+      "department": "Computer Science Engineering"
+    },
+     {
+      "id": "02", 
+      "name": "Raj", 
+      "department": "Mechanical Engineering"
+    }
+  }
+}
+```
+
+- Ouput
+
+```json
+{'id': '01', 'name': 'Yatharth', 'department': 'Computer Science Engineering'}
+{'id': '02', 'name': 'Raj', 'department': 'Mechanical Engineering'}
+```
+- `json.load()`: Reads JSON data from a file object and deserializes it into a Python object.
+- `json.loads()`: Deserializes JSON data from a string into a Python object.
+<hr>
+
+### Addtiotnal Context
+Relation between python data types and json data types is given in table below.
+</br>
+
+| Python Object   | JSON Object |
+|-----------------|-------------|
+| Dict            | object      |
+| list, tuple     | array       |
+| str             | string      |
+| int, long, float | numbers    |
+| True            | true        |
+| False           | false       |
+| None            | null        |
+
+
+
+## 3. Python Dictionary to JSON String
+- Parsing python dictionary to json string using `json.dumps()`.
+- Example Code:
+```python
+import json 
+    
+# Data to be written 
+dictionary ={ 
+  "id": "03", 
+  "name": "Suraj", 
+  "department": "Civil Engineering"
+} 
+
+# Serializing json  
+json_object = json.dumps(dictionary, indent = 4) 
+print(json_object)
+```
+- Output:
+``` json
+{
+    "department": "Civil Engineering",
+    "id": "02",
+    "name": "Suraj"
+}
+```
+## 4. Python Dictionary to JSON file.
+- - Parsing python dictionary to json string using `json.dump()`.
+- Example Code:
+``` python
+import json
+
+# Data to be written
+dictionary ={
+	"name" : "Satyendra",
+	"rollno" : 51,
+	"cgpa" : 8.8,
+	"phonenumber" : "123456789"
+}
+
+with open("sample.json", "w") as outfile:
+	json.dump(dictionary, outfile)
+
+```
+- Ouput: `sample.json`
+``` json
+{
+	"name" : "Satyendra",
+	"rollno" : 51,
+	"cgpa" : 8.8,
+	"phonenumber" : "123456789"
+}
+
+```
+## 5. Append Python Dictionary to JSON String.
+- Append to an already existing string using `json.update()`.
+- Example :
+```python
+import json
+# JSON data:
+x = { 
+  "id": "03", 
+  "name": "Suraj"
+} 
+
+# python object to be appended
+y = { "department": "Civil Engineering"}
+
+# parsing JSON string:
+z = json.loads(x)
+
+# appending the data
+z.update(y)
+
+# the result is a JSON string:
+print(json.dumps(z))
+
+```
+- Ouput:
+```json
+{"id": "03", "name": "Suraj", "department": "Civil Engineering"} 
+```
+
+
+## 6. Append Python Dictionary to JSON File.
+- 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.
+- `data.json`
+``` json
+{
+  "students":{
+    {
+      "id": "01", 
+      "name": "Yatharth", 
+      "department": "Computer Science Engineering"
+    },
+     {
+      "id": "02", 
+      "name": "Raj", 
+      "department": "Mechanical Engineering"
+    } 
+  }
+}
+```
+- Example Code:
+``` python
+import json
+
+# function to add to JSON
+def write_json(new_data, filename='data.json'):
+    with open(filename,'r+') as file:
+        # First we load existing data into a dict.
+        file_data = json.load(file)
+        # Join new_data with file_data inside students
+        file_data["students"].append(new_data)
+        # Sets file's current position at offset.
+        file.seek(0)
+        # convert back to json.
+        json.dump(file_data, file, indent = 4)
+
+# python object to be appended
+y = { 
+  "id": "03", 
+  "name": "Suraj", 
+  "department": "Civil Engineering"
+} 
+    
+write_json(y) 
+
+```
+- Output:
+```json
+{
+  "students":{
+    {
+      "id": "01", 
+      "name": "Yatharth", 
+      "department": "Computer Science Engineering"
+    },
+     {
+      "id": "02", 
+      "name": "Raj", 
+      "department": "Mechanical Engineering"
+    },
+    { 
+      "id": "03", 
+      "name": "Suraj", 
+      "department": "Civil Engineering"
+    } 
+  }
+}
+```
+
+</br>
+<hr>
+
+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.