with — Intermediate Examples

class Connection:
    def __init__(self, name):
        self.name = name
    def __enter__(self):
        print(f"  Connect to {self.name}")
        return self
    def __exit__(self, *args):
        print(f"  Disconnect from {self.name}")

# Multiple context managers
with Connection("db") as db, Connection("cache") as cache:
    print(f"Using {db.name} and {cache.name}")

print()

# contextlib.contextmanager decorator
from contextlib import contextmanager

@contextmanager
def timer(label):
    import time
    start = time.perf_counter()
    try:
        yield
    finally:
        elapsed = time.perf_counter() - start
        print(f"{label}: {elapsed:.6f}s")

with timer("Sum"):
    total = sum(range(1_000_000))
    print(f"Total: {total}")