Rename a folder of photos

Goal

Read a folder your phone filled with camera names, work out each photo's date from its name, plan readable new names and rename the files for real, leaving videos and notes alone.

Why it matters

Renaming files is the first automation most people actually need. You'll slice strings, filter with a rule, number things with enumerate and touch real files with the os module.

What it proves

You can turn a repetitive computer chore into a script that does it safely in one go.

Steps · 6 checkpoints

Each step is one function in rename_photos.py. In the workspace, press Check next to a step: it runs your file and tells you exactly what is still wrong. Step 1 is free; the rest are part of Pro or your 7-day free trial.

1. 1Find the date in the name. Write date_from_name(name): camera files carry the date in their name. IMG_20261001_4821.jpg was taken on 2026-10-01. Slice out the 8 digits after IMG_ and put dashes between year, month and day.
2. 2Build the new name. Write new_name(trip, date, n, ext): join the trip, the date and a 3-digit number with underscores, then the extension. new_name("Goa", "2026-10-01", 7, ".jpg") is Goa_2026-10-01_007.jpg.
3. 3Photos only. Write is_photo(name): True for names that start with IMG_ and end with .jpg, .jpeg or .png in any capitals (.JPG counts). notes.txt and the VID_ video must stay as they are.
4. 4Plan every rename. Write plan_renames(names, trip): a list of (old, new) pairs for the photos only, sorted by old name and numbered from 1. Keep each extension in lower case, so IMG_20261001_4828.JPG becomes Goa_2026-10-01_002.jpg.
5. 5Rename for real. Write apply_renames(folder, plan): rename each old file to its new name inside folder with os.rename (os.path.join builds the paths), then return how many you renamed. The check makes its own test folder.
6. 6Show the plan and rename. In main(), after the files are renamed, print one line per rename (old → new) and finish with Renamed 5 photos, left 2 other files alone. The check reads everything your program printed.

Requirements · rubric

Build against this exact list — it is the spec your published project is judged on.

• 01date_from_name() turns the camera name into YYYY-MM-DD
• 02is_photo() accepts .jpg/.jpeg/.png in any capitals and rejects everything else
• 03plan_renames() numbers the photos in sorted order and lower-cases the extension
• 04apply_renames() renames real files with os.rename and returns the count
• 05The program prints every rename and a summary line

Starter code

Copy this into a new file — or open it in a workspace as rename_photos.py. The TODO parts are yours to fill.

"""
Photo renamer.

Turns camera names like IMG_20261001_4821.jpg into Goa_2026-10-01_001.jpg
for every photo in a folder, and leaves other files alone. Fill in one
function per step, press Run, then press "Check" on that step.
"""
import os

TRIP = "Goa"

# What the phone dumped into the folder
FILES = [
    "IMG_20261002_0007.jpg",
    "IMG_20261001_4821.jpg",
    "notes.txt",
    "IMG_20261001_4828.JPG",
    "VID_20261002_0003.mp4",
    "IMG_20261003_1102.jpeg",
    "IMG_20261002_0011.png",
]


def date_from_name(name: str) -> str:
    # TODO: "IMG_20261001_4821.jpg" -> "2026-10-01".
    # The 8 digits after "IMG_" are the date: slice them out, then add dashes.
    raise NotImplementedError("step 1, date_from_name(): pull the date out of the name")


def new_name(trip: str, date: str, n: int, ext: str) -> str:
    # TODO: ("Goa", "2026-10-01", 7, ".jpg") -> "Goa_2026-10-01_007.jpg"
    # The number always has 3 digits: {n:03}
    raise NotImplementedError("step 2, new_name(): build the new file name")


def is_photo(name: str) -> bool:
    # TODO: True for camera photos: starts with IMG_ and ends with .jpg,
    # .jpeg or .png, in any capitals (.JPG counts). False for anything else.
    raise NotImplementedError("step 3, is_photo(): photos only")


def plan_renames(names: list[str], trip: str) -> list[tuple[str, str]]:
    # TODO: a list of (old name, new name) for the photos only, in sorted
    # order, numbered from 1. Keep each file's extension, in lower case.
    # Hint: os.path.splitext("a.JPG") -> ("a", ".JPG")
    raise NotImplementedError("step 4, plan_renames(): old name -> new name for every photo")


def apply_renames(folder: str, plan: list[tuple[str, str]]) -> int:
    # TODO: rename every file in the plan inside `folder` with os.rename,
    # then return how many files you renamed.
    raise NotImplementedError("step 5, apply_renames(): rename the files for real")


def main() -> None:
    sample = FILES[1]
    print(f"Example: {sample} → {new_name(TRIP, date_from_name(sample), 1, '.jpg')}")
    print(f"{sum(is_photo(f) for f in FILES)} of {len(FILES)} files are photos")
    # Given: make a folder with the phone's files in it.
    folder = "/tmp/trip-photos"
    os.makedirs(folder, exist_ok=True)
    for f in os.listdir(folder):
        os.remove(os.path.join(folder, f))
    for name in FILES:
        open(os.path.join(folder, name), "w").close()

    plan = plan_renames(os.listdir(folder), TRIP)
    done = apply_renames(folder, plan)
    # TODO: print one line per rename, "old → new" (loop over plan), then
    # "Renamed 5 photos, left 2 other files alone" using done.
    raise NotImplementedError("step 6, main(): print what was renamed")


if __name__ == "__main__":
    try:
        main()
    except NotImplementedError as todo:
        # A fresh starter is SUPPOSED to stop here. Say which step is next
        # instead of printing a traceback that looks like a bug.
        print(f"Not built yet: {todo}")
        print("Write that function, then press Run again. Each step you finish moves this message forward.")