Context Manager Mastery

Async contexts, ExitStack, and advanced patterns.

Overview

Master context manager patterns.

ExitStack Pattern

from contextlib import ExitStack

def process_files(filenames):
    with ExitStack() as stack:
        files = [
            stack.enter_context(open(fn, 'r'))
            for fn in filenames
        ]
        for f in files:
            print(f.read())

Async Context Manager

import asyncio
from contextlib import asynccontextmanager

@asynccontextmanager
async def async_resource(name):
    print(f"Acquiring {name}")
    await asyncio.sleep(0.1)
    resource = {"name": name, "active": True}
    try:
        yield resource
    finally:
        print(f"Releasing {name}")

async def main():
    async with async_resource("db") as db:
        print(f"Using {db}")

asyncio.run(main())

Practice

Implement a connection pool with async context managers.