Lesson 16 � Foundation

JSON:
DATA INTERCHANGE FORMAT.

JSON web APIs ki language hai � har website, har mobile app JSON use karta hai data bhejne ke liye. Python dictionaries aur JSON almost same hain. Ye lesson sikhaega ki Python mein JSON data ko kaise convert, read aur write karte hain.

WHY: JSON kyun zaroori hai?

Socho aap kisi website se data fetch kar rahe ho � weather app, news API, ya payment gateway. Sab kuch JSON format mein aata hai. Agar aapko web scraping, API integration, ya data storage karni hai toh JSON samajhna mandatory hai. Python ki dictionary aur JSON ki syntax almost same hai � isliye Python mein JSON handle karna bahut easy hai.

WHEN: kab use hota hai

JSON tab use hota hai jab aapko data exchange karna ho � web APIs se data fetch karna, user preferences save karna, configuration files rakhna, ya databases mein complex data store karna. Har modern web application JSON use karta hai.

HOW: JSON operations

Dictionary to JSON string

import json

student = {
 "name": "Aman",
 "age": 22,
 "skills": ["Python", "SQL"]
}

# Dictionary ✓ JSON string
json_string = json.dumps(student, indent=2)
print(json_string)
# {
# "name": "Aman",
# "age": 22,
# "skills": ["Python", "SQL"]
# }

print(type(json_string)) # <class 'str'>

json.dumps() dictionary ko JSON string mein convert karta hai. indent=2 se formatted output aata hai jo readable hota hai.

JSON string to dictionary

import json

json_string = '{"name": "Priya", "age": 21, "city": "Delhi"}'

# JSON string ✓ dictionary
data = json.loads(json_string)
print(data["name"]) # Priya
print(data["age"]) # 21

print(type(data)) # <class 'dict'>

json.loads() JSON string ko dictionary mein convert karta hai. Ab aap normal dictionary ki tarah data access kar sakte ho.

Read/write JSON files

import json

student = {"name": "Aman", "age": 22, "course": "Data Science"}

# Dictionary ✓ JSON file
with open("data.json", "w") as f:
 json.dump(student, f, indent=2)

# JSON file ✓ dictionary
with open("data.json", "r") as f:
 loaded = json.load(f)
 print(loaded)
 # {'name': 'Aman', 'age': 22, 'course': 'Data Science'}

json.dump() dictionary ko file mein write karta hai. json.load() file se dictionary read karta hai. Note: dumps (string) aur dump (file) mein fark hai.

JSON module ke useful functions

• json.dumps(obj) � object ko JSON string mein convert karta hai.
• json.loads(string) � JSON string ko Python object mein convert karta hai.
• json.dump(obj, file) � object ko JSON file mein write karta hai.
• json.load(file) � JSON file se Python object read karta hai.
• json.dumps(obj, indent=2) � formatted output deta hai, readable hota hai.
• json.dumps(obj, sort_keys=True) � keys ko alphabetical order mein sort karta hai.

JSON aur Python types

import json

# JSON types ✓ Python types mapping
data = {
 "string": "hello", # string ✓ str
 "number_int": 42, # number ✓ int
 "number_float": 3.14, # number ✓ float
 "boolean": True, # true ✓ True
 "null_value": None, # null ✓ None
 "list": [1, 2, 3], # array ✓ list
 "nested": {"key": "val"} # object ✓ dict
}

json_str = json.dumps(data)
parsed = json.loads(json_str)

print(parsed)
# Notice: True becomes true in JSON string
# But back in Python, it's True again

JSON mein true, false, null hote hain. Python mein ye True, False, None ban jaate hain. Dono taraf automatic conversion hota hai.

Common mistakes

• dumps aur dump mein confusion � dumps string return karta hai, dump file mein likhta hai.
• loads aur load mein confusion � loads string se padhta hai, load file se.
• JSON keys hamesha strings hoti hain � {"name": "Aman"} sahi hai, {name: "Aman"} galat hai.
• JSON mein trailing comma allowed nahi hai � {"a": 1,} error dega.
• Single quotes JSON mein allowed nahi hain � sirf double quotes use karo.