d1 = dict(a=1, b=3)
d2 = dict(a=2, b=4, c=6)

from collections import ChainMap

chain = ChainMap(d1, d2)
print(chain['a']) # -> 1
print(chain['c']) # -> 6

chain['c'] = -1
print(d1) # -> {'a': 1, 'b': 3, 'c': -1}
print(d2) # -> {'a': 2, 'b': 4, 'c': 6}

def handle_http_status(status_code):
    match status_code:
        case 200:
            return "Success!"
        case 400:
            return "Bad Request"

print(handle_http_status(200)) # -> Success!

def handle_http_status(status_code):
    match status_code:
        case 200:
            return "Success!"
        case 400:
            return "Bad Request"
        case _:
            return "Unknown Status"

def handle_http_status(status_code):
    match status_code:
        case 200:
            return "Success!"
        case 400 | 401 | 403 | 404:
            return "Client Error"

print(handle_http_status(404)) # -> Client Error

def handle_http_status(status_code):
    match status_code:
        case 200:
            return "Success!"
        case 400 | 401 | 403 | 404 as Err:
            return f"Client Error:{Err}"

print(handle_http_status(404)) # -> Client Error:404

def execute_command(command):
    match command:
        case ("print", message):
            print(f"{message}")
        case ["save", filename, data]:
            print(f"Saving {data} to {filename}")
        case ("delete", filename):
            print(f"Deleting {filename}")
        case ('todo', *something):
            print(f"To do: {' '.join(something)}")
        case _:
            print("Unknown Command")


execute_command(("print", "Hello, Yang Zhou!")) # -> Hello, Yang Zhou!

def handle_user_action(action):
    match action:
        case {"type": "login", "username": user, "password": pw}:
            return f"Login attempt by {user} with password {pw}"
        case {"type": "logout", "username": user}:
            return f"User {user} logged out"
        case {"type": "signup", "username": user, "email": email}:
            return f"New signup by {user} with email {email}"
        case _:
            return "Unknown action"


print(handle_user_action({"type": "login", "username": "Yang Zhou", "password": "123456"})) # -> Login attempt by Yang Zhou with password 123456

def handle_user_op(action):
    match action:
        case "login" if user_not_logged_in():
            return "User needs to log in"
        case "login":
            return "Already logged in"
        case "logout":
            return "Logging out"
        case _:
            return "Unknown action"

class Circle:
    def __init__(self, radius):
        self.radius = radius

class Rectangle:
    def __init__(self, length, width):
        self.length = length
        self.width = width

def process_shape(shape):
    match shape:
        case Circle(radius=r):
            return f"Processing a circle with radius {r}"
        case Rectangle(length=l, width=w):
            return f"Processing a rectangle with length {l} and width {w}"