Context Managers

The with statement guarantees setup and cleanup (files, locks, connections), even when errors occur.

Easy

from contextlib import contextmanager

@contextmanager
def powered(device):
    device.on()
    try:
        yield device
    finally:
        device.off()

with powered(motor) as m:
    m.run(5)

Class-based managers implement __enter__ and __exit__.

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