Advanced Python Features

1. Typing Overloads

In Python, @overload tells the type checker to expect different signatures for the same function. It doesn’t actually define multiple versions of the function itself, unlike Java or C++.

from typing import overload

@overload
def get_user(id: int = ..., username: None = None) -> User:
    ...

@overload
def get_user(id: None = None, username: str = ...) -> User:
    ...

def get_user(id: int | None = None, username: str | None = None) -> User:
    ...

2. Keyward-only & Positional-only Arguments

def foo(a, b, /, c, d, *, e, f):
	...

5. Protocol

from typing import Protocol

# Add the @runtime_checkable decorator if you want isinstance() checks to work
# alongside your Protocols!
@runtime_checkable
class Quackable(Protocol):
    def quack(self) -> None:
        ...  # The ellipsis indicates this is just a method signature

class Duck:
    def quack(self): print('Quack!')

class Dog:
    def bark(self): print('Woof!')

def run_quack(obj: Quackable):
    obj.quack()

run_quack(Duck())  # Works!
run_quack(Dog())  # Fails during TYPE CHECKING (and runtime)

6. Context Managers

# NEW SYNTAX - New contextlib-based context manager
import contextlib

@contextlib.contextmanager
def retry():
    print("Entering Context")
    yield
    print("Exiting Context")

9.2 Walrus Operator

if response := pattern.search(line):
    print('You pressed:', response)
else:
    print('You pressed nothing')