Python Args and Kwargs

In real projects, you often want functions that can accept:
- any number of positional values
- any number of keyword options

  That is what:
  - `*args` handles (positional arguments)
  - `**kwargs` handles (keyword arguments)
  
  ## *args (variable positional arguments)
  
  ```python
  def add_all(*args):
      print(args)       # shows it's a tuple
      return sum(args)
  
  print(add_all(1, 2, 3))
  print(add_all(1, 2, 3, 4, 5))
  ```
  
  Expected output:
  
  ```
  (1, 2, 3)
  6
  (1, 2, 3, 4, 5)
  15
  ```
  
  ## **kwargs (variable keyword arguments)
  
  ```python
  def print_info(**kwargs):
      print(kwargs)  # shows it's a dictionary
      for key, value in kwargs.items():
          print(f"{key}: {value}")
  
  print_info(name="Tom", city="Austin", age=25)
  ```
  
  Expected output:
  
  ```
  {'name': 'Tom', 'city': 'Austin', 'age': 25}
  name: Tom
  city: Austin
  age: 25
  ```
  
  ## Using both together
  
  ```python
  def make_user(name, *hobbies, **details):
      print(f"Name: {name}")
      print(f"Hobbies: {hobbies}")
      print(f"Details: {details}")
  
  make_user(
      "Sarah",
      "reading", "gaming",
      city="Seattle",
      age=28
  )
  ```
  
  Expected output:
  
  ```
  Name: Sarah
  Hobbies: ('reading', 'gaming')
  Details: {'city': 'Seattle', 'age': 28}
  ```
  
  ## Unpacking (very common in real code)
  
  ```python
  def greet(first, last):
      print(f"Hello {first} {last}!")
  
  names = ["Tom", "Smith"]
  greet(*names)
  
  person = {"first": "Sarah", "last": "Johnson"}
  greet(**person)
  ```
  
  Expected output:
  
  ```
  Hello Tom Smith!
  Hello Sarah Johnson!
  ```
  
  ## Graph: argument flow
  
  ```mermaid
  flowchart LR
    A[Call site] --> B[*args tuple]
    A --> C[**kwargs dict]
    B --> D[Function receives arguments]
    C --> D
  ```
  
  ## Best practice rule
  
  Use `*args` and `**kwargs` to make APIs flexible, but do not use them to hide unclear function design.
  If a function expects a specific argument, name it directly.
  
  In the next lesson, you will learn type hints, which improves clarity and helps tools catch mistakes earlier.