Contextlib - Context Managers

Introduction

The contextlib module provides utilities for working with context managers. It includes decorators like @contextmanager and @closing that simplify creating and using context managers.

@contextmanager Decorator

from contextlib import contextmanager

@contextmanager
def managed_resource():
    resource = acquire_resource()
    try:
        yield resource
    finally:
        release_resource(resource)

with managed_resource() as r:
    r.use()

@closing Decorator

from contextmanager import closing
from urllib.request import urlopen

with closing(urlopen("http://example.com")) as page:
    content = page.read()

Nested Context Managers

from contextlib import ExitStack

with ExitStack() as stack:
    file1 = stack.enter_context(open("file1.txt"))
    file2 = stack.enter_context(open("file2.txt"))

Context Manager for Timing

import time
from contextlib import contextmanager

@contextmanager
def timer(name):
    start = time.time()
    yield
    print(f"{name} took {time.time() - start:.2f}s")

with timer("operation"):
    perform_operation()

Practice Problems

1. Create a context manager for database connections
2. Implement a timing context manager
3. Use @closing with a network resource
4. Create nested context managers
5. Implement a retry context manager