stop using os.path, use pathlib

2025-12-09

pathlib has been in the stdlib since Python 3.4. I kept typing os.path.join out of muscle memory for years after that. Last year I made myself stop. Should have done it sooner.

compare

import os
cfg = os.path.join(os.path.dirname(__file__), "..", "config", "settings.json")
with open(cfg) as f:
    data = json.load(f)

from pathlib import Path
cfg = Path(__file__).parent.parent / "config" / "settings.json"
data = json.loads(cfg.read_text())

The / operator reads like a path. .parent.parent reads like what it is. .read_text() replaces the open-with-context dance when you just want the contents.

the five methods I use most

Path("a/b/c").exists()
Path("dir").mkdir(parents=True, exist_ok=True)
Path("file").write_text("hello")
Path(".").glob("**/*.py") — walks the tree
Path("x.log").with_suffix(".gz") — returns x.gz without rebuilding the string

when to still use os

Two cases: low-level file ops where you need flags (os.open with O_EXCL), or when a library you're calling demands a string. For the string case, pass str(path) and move on.

minor annoyance

Some stdlib functions don't accept Path objects until later Python versions. It's rare now but if you see a mysterious type error, that's the fix.