Context Managers (with)

Definition

A context manager sets up and tears down a resource automatically using the with statement.

Guarantees files, locks and connections are closed even on errors.

Diagram

Flowchart

Example: Custom context manager

from contextlib import contextmanager
@contextmanager
def tag(n):
    print(f'<{n}>'); yield; print(f'</{n}>')
with tag('b'):
    print('hi')

Output: <b> hi </b>

Key points

• Always open files with with
• contextlib simplifies writing them

Interview questions

More Python topics