All 15 File I/O & Context Managers questions
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How do you write and use a custom context manager by implementing __enter__ and __exit__? 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 would you implement a context manager that temporarily changes the current working directory and restores it afterward? 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?
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Python › File I/O & Context Managers

How do you check whether a file or directory exists before operating on it, using pathlib?

Intermediate

Answer

Path.exists() returns True if the path exists at all (file or directory); Path.is_file() and Path.is_dir() narrow the check to specifically a regular file or a directory respectively, letting you branch logic based on exactly what kind of filesystem entry is present.
from pathlib import Path

p = Path("data.txt")
if p.exists() and p.is_file():
    content = p.read_text()
else:
    print("File not found")
Real-world example Checking whether a configuration file exists before attempting to read it, falling back to defaults if it doesn't.

Common follow-ups: Is there a race condition risk between checking p.exists() and later opening the file, and how would EAFP-style code avoid it?

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