python-development

Python 开发

Python 语言核心概念、惯用法和最佳实践。

何时使用此技能

适用情况……	以下情况请改用专门的同类技能……
编写符合惯例的 Python 3.10+ 代码（match 语句、结构化模式匹配、PEP 604 联合类型）	运行单个脚本或一次性命令——使用 uv-run
为库代码添加类型提示、装饰器或上下文管理器	初始化项目或添加依赖项——使用 uv-project-management
设计 async/await 流程，或重构为符合 Python 惯例的模式	编写或运行 pytest 测试——使用 python-testing

核心专长

• Python 语言：现代 Python 3.10+ 特性和惯用法
• 最佳实践：Pythonic 代码、设计模式、SOLID 原则
• 调试：交互式调试和性能分析技术
• 性能：优化策略和性能分析
• 异步编程：async/await 模式和 asyncio

现代 Python 特性（3.10+）

类型提示

# Modern syntax (Python 3.10+)
def process_items(
    items: list[str],                    # Not List[str]
    mapping: dict[str, int],             # Not Dict[str, int]
    optional: str | None = None,         # Not Optional[str]
) -> tuple[bool, str]:                   # Not Tuple[bool, str]
    """Process items with modern type hints."""
    return True, "success"

# Type aliases
type UserId = int
type UserDict = dict[str, str | int]

def get_user(user_id: UserId) -> UserDict:
    return {"id": user_id, "name": "Alice"}

模式匹配（3.10+）

def handle_command(command: dict) -> str:
    match command:
        case {"action": "create", "item": item}:
            return f"Creating {item}"
        case {"action": "delete", "item": item}:
            return f"Deleting {item}"
        case {"action": "list"}:
            return "Listing items"
        case _:
            return "Unknown command"

结构化模式匹配

def process_response(response):
    match response:
        case {"status": 200, "data": data}:
            return process_success(data)
        case {"status": 404}:
            raise NotFoundError()
        case {"status": code} if code >= 500:
            raise ServerError(code)

Python 惯用法

上下文管理器

# File handling
with open("file.txt") as f:
    content = f.read()

# Custom context manager
from contextlib import contextmanager

@contextmanager
def database_connection():
    conn = create_connection()
    try:
        yield conn
    finally:
        conn.close()

with database_connection() as conn:
    conn.execute("SELECT * FROM users")

列表推导式

# List comprehension
squares = [x**2 for x in range(10)]

# Dict comprehension
word_lengths = {word: len(word) for word in ["hello", "world"]}

# Set comprehension
unique_lengths = {len(word) for word in ["hello", "world", "hi"]}

# Generator expression
sum_of_squares = sum(x**2 for x in range(1000000))  # Memory efficient

迭代器和生成器

def fibonacci():
    a, b = 0, 1
    while True:
        yield a
        a, b = b, a + b

# Use generator
fib = fibonacci()
first_ten = [next(fib) for _ in range(10)]

# Generator expression
even_squares = (x**2 for x in range(10) if x % 2 == 0)

调试

交互式调试

import pdb

def problematic_function():
    value = calculate()
    pdb.set_trace()  # Debugger breakpoint
    return process(value)

# Debug on error
python -m pdb script.py

# pytest with debugger
uv run pytest --pdb                     # Drop into pdb on failure
uv run pytest --pdb --pdbcls=IPython.terminal.debugger:TerminalPdb

性能分析

# CPU profiling
uv run python -m cProfile -s cumtime script.py | head -20

# Line-by-line profiling (temporary dependency)
uv run --with line-profiler kernprof -l -v script.py

# Memory profiling (temporary dependency)
uv run --with memory-profiler python -m memory_profiler script.py

# Real-time profiling (ephemeral tool)
uvx py-spy top -- python script.py

# Quick profiling with scalene
uv run --with scalene python -m scalene script.py

内置调试工具

# Trace execution
import sys

def trace_calls(frame, event, arg):
    if event == 'call':
        print(f"Calling {frame.f_code.co_name}")
    return trace_calls

sys.settrace(trace_calls)

# Memory tracking
import tracemalloc

tracemalloc.start()
# ... code to profile
snapshot = tracemalloc.take_snapshot()
top_stats = snapshot.statistics('lineno')
for stat in top_stats[:10]:
    print(stat)

异步编程

基本 async/await

import asyncio

async def fetch_data(url: str) -> dict:
    async with httpx.AsyncClient() as client:
        response = await client.get(url)
        return response.json()

async def main():
    result = await fetch_data("https://api.example.com")
    print(result)

asyncio.run(main())

并发任务

async def process_multiple():
    # Run concurrently
    results = await asyncio.gather(
        fetch_data("url1"),
        fetch_data("url2"),
        fetch_data("url3"),
    )
    return results

# With timeout
async def with_timeout():
    try:
        result = await asyncio.wait_for(fetch_data("url"), timeout=5.0)
    except asyncio.TimeoutError:
        print("Request timed out")

设计模式

依赖注入

from typing import Protocol

class Database(Protocol):
    def query(self, sql: str) -> list: ...

def get_users(db: Database) -> list:
    return db.query("SELECT * FROM users")

工厂模式

def create_handler(handler_type: str):
    match handler_type:
        case "json":
            return JSONHandler()
        case "xml":
            return XMLHandler()
        case _:
            raise ValueError(f"Unknown handler: {handler_type}")

装饰器模式

from functools import wraps
import time

def timer(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        end = time.time()
        print(f"{func.__name__} took {end - start:.2f}s")
        return result
    return wrapper

@timer
def slow_function():
    time.sleep(1)

最佳实践

SOLID 原则

单一职责：

# Bad: Class does too much
class User:
    def save(self): pass
    def send_email(self): pass
    def generate_report(self): pass

# Good: Separate concerns
class User:
    def save(self): pass

class EmailService:
    def send_email(self, user): pass

class ReportGenerator:
    def generate(self, user): pass

快速失败

def process_data(data: dict) -> str:
    # Validate early
    if not data:
        raise ValueError("Data cannot be empty")
    if "required_field" not in data:
        raise KeyError("Missing required field")

    # Process with confidence
    return data["required_field"].upper()

函数式方法

# Prefer immutable transformations
def process_items(items: list[int]) -> list[int]:
    return [item * 2 for item in items]  # New list

# Over mutations
def process_items_bad(items: list[int]) -> None:
    for i in range(len(items)):
        items[i] *= 2  # Mutates input

项目结构（src 布局）

my-project/
├── pyproject.toml
├── README.md
├── src/
│   └── my_project/
│       ├── __init__.py
│       ├── core.py
│       ├── utils.py
│       └── models.py
└── tests/
    ├── conftest.py
    ├── test_core.py
    └── test_utils.py

另请参阅

• uv-run - 运行脚本、临时依赖项、PEP 723
• uv-project-management - 项目设置和依赖项管理
• uv-tool-management - 全局安装 CLI 工具
• python-testing - 使用 pytest 进行测试
• python-code-quality - 使用 ruff/ty 进行代码检查和类型检查
• python-packaging - 构建和发布包
• uv-python-versions - 管理 Python 解释器

参考资料

• Python 文档：https://docs.python.org/3/
• 类型提示：https://docs.python.org/3/library/typing.html
• 异步编程：https://docs.python.org/3/library/asyncio.html
• 详细指南：请参阅 REFERENCE.md