Py Context Managers Custom — Free Python Tutorial

TL;DR: Learn Py Context Managers Custom in Python with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.

Py Context Managers Custom in Python

A context manager controls resource acquisition and release using the with statement. Python calls __enter__ when entering the block and __exit__ when leaving — even if an exception occurs. This guarantees cleanup.

The most common example is open(): it acquires a file handle on __enter__ and closes it on __exit__. Without with, forgetting f.close() causes file descriptor leaks.

You can write custom context managers two ways: (1) a class with __enter__ / __exit__ methods, or (2) a generator function decorated with @contextlib.contextmanager — the yield separates setup from teardown.

Practical uses: database transactions (commit/rollback), timing code blocks, temporary directory creation, mocking in tests, suppressing specific exceptions with contextlib.suppress().

# Class-based context manager
class CM:
    def __enter__(self):
        # setup
        return resource
    def __exit__(self, exc_type, exc_val, exc_tb):
        # teardown — return True to suppress exceptions

# Generator-based (simpler)
from contextlib import contextmanager
@contextmanager
def cm():
    # setup
    yield resource
    # teardown

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