Files and Folders with pathlib

Files and Folders with pathlib

Automating starts with handing repetitive file handling over to Python: sorting exports, renaming reports, merging the month’s files. The standard pathlib module makes these operations simple and portable.

Portable paths

from pathlib import Path

dossier = Path("rapports") / "2026"          # the / operator joins the pieces
fichier = dossier / "ventes_novembre.csv"
print(fichier)            # rapports/2026/ventes_novembre.csv (or with \ on Windows)

print(fichier.name)       # ventes_novembre.csv
print(fichier.stem)       # ventes_novembre
print(fichier.suffix)     # .csv
print(fichier.parent)     # rapports/2026
print(fichier.with_suffix(".xlsx").name)  # ventes_novembre.xlsx

Path.cwd()                # current working directory
Path.home()               # the user's home directory

No more concatenating strings with "/" or "\\": pathlib picks the right separator for the system.

Reading and writing text

notes = Path("notes.txt")
notes.write_text("Première ligne\nDeuxième ligne\n", encoding="utf-8")
contenu = notes.read_text(encoding="utf-8")
print(contenu.splitlines())   # ['Première ligne', 'Deuxième ligne']

# To read or write as you go, line by line:
with notes.open("a", encoding="utf-8") as f:   # "a": append to the end of the file
    f.write("Troisième ligne\n")

with notes.open(encoding="utf-8") as f:        # read by default ("r")
    for ligne in f:
        print(ligne.rstrip("\n"))

The with block closes the file automatically, even on error. Always specify encoding="utf-8": before Python 3.15, the default encoding depends on the system (often different on Windows), a classic source of unreadable accented characters. Python 3.15 uses UTF-8 by default everywhere, but specifying it remains the rule: the intent is explicit and the code behaves the same way with earlier versions. The modes: "r" read, "w" write (overwrites!), "a" append, "x" create (error if the file exists).

Browsing a folder

exports = Path("exports")
for chemin in sorted(exports.glob("*.csv")):      # .csv files in the folder
    print(chemin.name, chemin.stat().st_size, "bytes")

tous = list(exports.rglob("*.csv"))               # rglob: also in subfolders
dossiers = [p for p in exports.iterdir() if p.is_dir()]

Creating, moving, organizing

archive = Path("archive") / "2026-11"
archive.mkdir(parents=True, exist_ok=True)   # also creates parents, no error if it exists

for chemin in Path("exports").glob("*.csv"):
    destination = archive / chemin.name
    chemin.replace(destination)               # moves (and overwrites if the target exists)

chemin.unlink() deletes a file; for a non-empty folder, the shutil module offers shutil.rmtree and shutil.copy2 to copy. Be careful: a delete or move loop acts on hundreds of files in a second. Always test your script on a temporary folder:

import tempfile
with tempfile.TemporaryDirectory() as tmp:
    base = Path(tmp)
    (base / "essai.csv").write_text("a,b\n1,2\n", encoding="utf-8")
    print([p.name for p in base.iterdir()])
# the temporary folder and its contents are deleted on leaving the block

This is exactly what the exercises in this lesson do.

Key takeaways

• Path + / for portable paths; name, stem, suffix, parent.
• read_text / write_text or with open(...), always with encoding="utf-8".
• glob, mkdir(parents=True, exist_ok=True), replace; test on a temporary folder.