Pathlib Competent¶

🐍 Core Python Track · Level 2

⏱️ ~2 days 📚 Prerequisite: File Handling

pathlib.Path is the modern, object-oriented way to work with filesystem paths. It replaces most of os.path with cleaner, cross-platform code.

Building paths¶

Building paths in Pathlib — what it is and when to use it.

The / operator joins path segments — no manual separators:

from pathlib import Path

p = Path("project") / "src" / "main.py"
print(p.as_posix())   # project/src/main.py  (forward slashes on any OS)

Inspecting a path¶

Inspecting a path in Pathlib — what it is and when to use it.

from pathlib import PurePosixPath

p = PurePosixPath("/home/user/report.final.txt")
print(p.name)      # report.final.txt
print(p.stem)      # report.final
print(p.suffix)    # .txt
print(p.suffixes)  # ['.final', '.txt']
print(p.parent.as_posix())   # /home/user
print(p.parts)     # ('/', 'home', 'user', 'report.final.txt')

parts and the root differ by OS

This uses PurePosixPath so the output is identical everywhere. A plain Path on Windows would show a '\\' root segment. For OS-agnostic examples, PurePosixPath / PureWindowsPath let you reason about paths without touching the real filesystem.

Changing parts¶

Changing parts in Pathlib — what it is and when to use it.

from pathlib import Path

p = Path("data/input.csv")
print(p.with_suffix(".json").as_posix())   # data/input.json
print(p.with_name("output.csv").as_posix())  # data/output.csv
print(p.with_stem("final").as_posix())       # data/final.csv  (3.9+)

Current, home, absolute¶

Current, home, absolute in Pathlib — what it is and when to use it.

from pathlib import Path

print(Path.cwd().is_absolute())    # True
print(Path.home().is_absolute())   # True
print(Path("x").resolve().is_absolute())   # True

Existence & type checks¶

Existence & type checks in Pathlib — what it is and when to use it.

from pathlib import Path

p = Path(".")
print(p.exists())    # True
print(p.is_dir())    # True
print(p.is_file())   # False

Reading & writing (one-liners)¶

Reading & writing (one-liners) in Pathlib — what it is and when to use it.

from pathlib import Path
import tempfile

d = Path(tempfile.mkdtemp())
f = d / "note.txt"

f.write_text("hello", encoding="utf-8")   # returns chars written
print(f.read_text(encoding="utf-8"))      # hello

f.write_bytes(b"\x00\x01")
print(f.read_bytes())                      # b'\x00\x01'

Globbing¶

Globbing in Pathlib — what it is and when to use it.

from pathlib import Path
import tempfile

d = Path(tempfile.mkdtemp())
(d / "a.py").write_text("")
(d / "b.py").write_text("")
(d / "c.txt").write_text("")

py = sorted(p.name for p in d.glob("*.py"))
print(py)   # ['a.py', 'b.py']

Use rglob("*.py") for a recursive search through all subdirectories.

Creating & removing¶

Creating & removing in Pathlib — what it is and when to use it.

from pathlib import Path
import tempfile

base = Path(tempfile.mkdtemp())
nested = base / "x" / "y"
nested.mkdir(parents=True, exist_ok=True)   # make intermediate dirs
print(nested.exists())   # True

f = nested / "t.txt"
f.write_text("x")
f.unlink()               # delete the file
print(f.exists())        # False

Prefer pathlib over os.path

Path("a") / "b" is clearer and OS-agnostic versus os.path.join("a", "b"), and the read/write one-liners replace boilerplate open(...) blocks for small files.

Practice exercises¶

Given a path, print its extension and the filename without extension.
Count all .md files under a directory tree using rglob.
Build a path to ~/.config/app/settings.json using Path.home().
Write and then read back a text file using only Path methods.

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