python

Python

Overview

Modern Python development patterns including type hints, async programming, and Pythonic idioms.

---

Type Hints

Basic Types

from typing import (
    Optional, Union, List, Dict, Set, Tuple,
    TypeVar, Generic, Callable, Any,
    Literal, TypedDict, Protocol
)
from dataclasses import dataclass
from datetime import datetime

# Basic type hints
def greet(name: str) -> str:
    return f"Hello, {name}!"

# Optional (can be None)
def find_user(user_id: str) -> Optional['User']:
    return users.get(user_id)

# Union types
def process(value: Union[str, int]) -> str:
    return str(value)

# Python 3.10+ union syntax
def process_new(value: str | int | None) -> str:
    return str(value) if value else ""

# Collections
def process_items(
    items: List[str],
    mapping: Dict[str, int],
    unique: Set[str],
    pair: Tuple[str, int]
) -> None:
    pass

# Python 3.9+ built-in generics
def process_items_new(
    items: list[str],
    mapping: dict[str, int],
    unique: set[str]
) -> None:
    pass

Advanced Types

# TypeVar for generics
T = TypeVar('T')
K = TypeVar('K')
V = TypeVar('V')

def first(items: list[T]) -> T | None:
    return items[0] if items else None

# Generic classes
class Repository(Generic[T]):
    def __init__(self) -> None:
        self._items: dict[str, T] = {}

    def get(self, id: str) -> T | None:
        return self._items.get(id)

    def save(self, id: str, item: T) -> None:
        self._items[id] = item

# TypedDict for structured dicts
class UserDict(TypedDict):
    id: str
    name: str
    email: str
    age: int  # Required
    nickname: str  # Required

class PartialUserDict(TypedDict, total=False):
    nickname: str  # Optional

# Literal types
Mode = Literal["read", "write", "append"]

def open_file(path: str, mode: Mode) -> None:
    pass

# Protocol (structural typing)
class Readable(Protocol):
    def read(self) -> str: ...

def process_readable(source: Readable) -> str:
    return source.read()

# Callable types
Handler = Callable[[str, int], bool]
AsyncHandler = Callable[[str], 'Awaitable[bool]']

def register_handler(handler: Handler) -> None:
    pass