Python JSON Handling

JSON is the most common data format used by APIs. If you work with web services, you will see JSON daily.

  Important concept:
  - In Python, JSON maps naturally to dictionaries and lists.
  - JSON object → Python dict
  - JSON array → Python list
  
  ## Python object to JSON string
  
  ```python
  import json
  
  person = {
      "name": "Alice",
      "age": 28,
      "city": "Portland"
  }
  
  json_string = json.dumps(person)
  print(json_string)
  ```
  
  Expected output:
  
  ```
  {"name": "Alice", "age": 28, "city": "Portland"}
  ```
  
  ### Pretty print JSON (good for debugging)
  
  ```python
  json_pretty = json.dumps(person, indent=2)
  print(json_pretty)
  ```
  
  Expected output:
  
  ```
  {
    "name": "Alice",
    "age": 28,
    "city": "Portland"
  }
  ```
  
  ## JSON string to Python object
  
  ```python
  import json
  
  json_string = '{"name": "Bob", "age": 30}'
  person = json.loads(json_string)
  
  print(person)
  print(person["name"])
  ```
  
  Expected output:
  
  ```
  {'name': 'Bob', 'age': 30}
  Bob
  ```
  
  ## Read JSON from a file (load)
  
  ```python
  import json
  
  with open("data.json", "r") as file:
      data = json.load(file)
  
  print(data)
  ```
  
  ## Write JSON to a file (dump)
  
  ```python
  import json
  
  data = {
      "users": [
          {"name": "Tom", "city": "Austin"},
          {"name": "Sarah", "city": "Miami"}
      ]
  }
  
  with open("users.json", "w") as file:
      json.dump(data, file, indent=2)
  ```
  
  ## dumps vs dump (simple rule)
  
  - `dumps()` → returns a **string**
  - `dump()` → writes to a **file**
  
  - `loads()` → converts a **string**
  - `load()` → reads from a **file**
  
  ## Graph: JSON flow in real projects
  
  ```mermaid
  flowchart LR
    A[Python dict/list] -->|json.dumps| B[JSON string]
    B -->|send to API| C[Network]
    C -->|receive JSON| D[JSON string]
    D -->|json.loads| E[Python dict/list]
  ```
  
  ## Practical tip: JSON numbers, booleans, null
  
  - JSON `true/false` → Python `True/False`
  - JSON `null` → Python `None`
  
  If you see `None`, that often means “missing” or “no value”.
  
  In the next lesson, you will learn datetime, because handling dates correctly is a real-world skill in APIs, databases, and logs.