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How does @contextlib.contextmanager let you write a context manager using a generator function instead of a full class? How do you use pathlib.Path for modern, object-oriented file path manipulation instead of os.path's string-based functions? How do you use multiple context managers in a single 'with' statement, and how does this compare to nesting separate 'with' blocks? How do you check whether a file or directory exists before operating on it, using pathlib? How do you implement contextlib.ExitStack to dynamically manage a VARIABLE number of context managers determined at runtime? How would you write a reusable context manager decorator using contextlib.contextmanager that ALSO works when applied directly to a function, like @contextmanager-decorated functions support? How would you implement a context manager for managing a lock (like threading.Lock) while ALSO adding a timeout, raising an error if the lock can't be acquired quickly enough? How do you correctly handle character encoding when reading text files that might not be UTF-8, and what error occurs if you guess wrong? How would you implement asynchronous file I/O using aiofiles alongside an async context manager, to avoid blocking the event loop during file operations? How would you write a context manager that atomically writes to a file, avoiding leaving a corrupted or partially-written file if an exception occurs mid-write?
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Python › File I/O & Context Managers

How would you implement a context manager that temporarily changes the current working directory and restores it afterward?

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Answer

Save the ORIGINAL working directory in __enter__ before changing to the new one, then restore it in __exit__ (or the equivalent finally block in a @contextmanager generator) — ensuring the change is always reverted even if an exception occurs while the directory is temporarily changed.
import os
from contextlib import contextmanager

@contextmanager
def temporary_directory(path):
    original = os.getcwd()
    os.chdir(path)
    try:
        yield
    finally:
        os.chdir(original)  # always restored, even on exception

with temporary_directory("/tmp"):
    process_files_here()
# working directory is back to the original, guaranteed
Real-world example Running a subprocess or script that requires a specific working directory, without permanently affecting the calling code's environment.

Common follow-ups: Why is this pattern particularly risky to implement WITHOUT a context manager, in terms of leaking the directory change on error?

Exception Handling
All 15 File I/O & Context Managers questions