Automating files

Part of the free LogicWiz Python course, Pack B: College Semester Pack. The examples and practice run in the app.

Meher's Downloads folder has 300 files: lecture PDFs, WhatsApp photos, marks(3).csv. Sorting them by hand takes an evening. A 10-line Python script does it in a second, and it's a lab program too.

You'll learn to

• List, inspect and build paths with `os` and `os.path`
• Copy, move and rename with `shutil` and `os`, and make folders
• Walk a whole folder tree with `os.walk`, and zip files with `zipfile`

Learn

Your toolbox

Here the files live in the browser's own pretend disk, so nothing on your phone is touched.

Look inside a folder

import os

folder = "downloads"
for name in sorted(os.listdir(folder)):
    path = os.path.join(folder, name)
    base, ext = os.path.splitext(name)
    print(f"{name:<18} ext={ext or '(none)':<7} {os.path.getsize(path)} bytes")

os.listdir gives just the names, in no promised order, so we sort them and join the folder back on before using a name as a path.

Sort files into folders by type

import os
import shutil

folder = "downloads"
for name in os.listdir(folder):
    path = os.path.join(folder, name)
    if not os.path.isfile(path):
        continue
    ext = os.path.splitext(name)[1].lower().lstrip(".") or "others"
    target = os.path.join(folder, ext)
    os.makedirs(target, exist_ok=True)
    shutil.move(path, os.path.join(target, name))

for sub in sorted(os.listdir(folder)):
    print(sub + "/", sorted(os.listdir(os.path.join(folder, sub))))

.lower() puts timetable.PDF with the other PDFs. exist_ok=True means "fine if the folder is already there". Copy instead of move with shutil.copy.

os.walk: every folder, every file

import os

for folder, subfolders, files in os.walk("college"):
    subfolders.sort()                       # walk in a fixed order
    depth = folder.count(os.sep)
    print("  " * depth + os.path.basename(folder) + "/")
    for f in sorted(files):
        print("  " * (depth + 1) + f)

For each folder under the top, os.walk gives a triple: the folder's path, the names of its subfolders, and the names of its files. Sorting subfolders in place also fixes the order it walks them.

Zip a backup

import os
import zipfile

with zipfile.ZipFile("lab_backup.zip", "w") as z:
    for folder, _, files in os.walk("labs"):
        for f in files:
            if f.endswith(".py"):
                path = os.path.join(folder, f)
                z.write(path, arcname=os.path.relpath(path, "labs"))

with zipfile.ZipFile("lab_backup.zip") as z:
    print(sorted(z.namelist()))
    print(z.read("week1/hello.py").decode())

arcname is the name inside the zip; relpath keeps it short (week1/hello.py, not labs/week1/hello.py). Open with "r" (the default) to read, "w" to create, "a" to add.

Deleting is forever. os.remove(file) and shutil.rmtree(folder) skip the Recycle Bin. When you write a cleanup script, first run it with the delete line replaced by a print("would delete", path) (a dry run), check the list, then switch it on. And never assume os.listdir order: always sorted(...).

Lab mapping. VTU's Python course is built on Automate the Boring Stuff, and its "organising files" unit is exactly this lesson: shutil copy/move/rename, os.walk, and zipfile. File-handling programs (list a folder, count files by type, copy or back up files) also appear in AKTU, JNTU, Anna, DU and Mumbai labs.

Viva: "Difference between os.listdir and os.walk?" (one folder vs the whole tree) "Why os.path.join instead of + "/"?" (it uses the right separator on every OS) "shutil.copy vs shutil.move?"

In one line

os.listdir gives names (join them back with os.path.join); os.walk visits the whole tree; shutil.copy/move and os.makedirs(exist_ok=True) organise; zipfile backs up; deleting is permanent.