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Level 1 / Project 13 - Batch Rename Simulator

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Concept This project — Quiz Flashcards — Browser

Estimated time: 35 minutes

Focus

  • safe rename planning without destructive changes

Why this project exists

Plan file renames without actually moving anything. Apply rules like lowercase, strip-numbers, or add-prefix, detect naming conflicts, and preview a before/after mapping. You will learn safe simulation before destructive operations.

Run (copy/paste)

Use <repo-root> as the folder containing this repository's README.md.

cd <repo-root>/projects/level-1/13-batch-rename-simulator
python project.py --input data/sample_input.txt --rule lower
pytest -q

Expected terminal output

=== Batch Rename Plan (rule: lower) ===

  001_Project Report.docx      => 001_project report.docx
  002_Meeting Notes.txt        => 002_meeting notes.txt
  003_Budget Spreadsheet.xlsx  => 003_budget spreadsheet.xlsx

  3 renames planned, 0 conflicts
8 passed

Expected artifacts

  • data/output.json
  • Passing tests
  • Updated notes.md

Checkpoint: Baseline code runs and all tests pass. Commit your work before continuing.

Alter it (required) — Extension

  1. Add a new rule: add_date that prepends today's date as YYYY-MM-DD_ to the filename.
  2. Add a --dry-run flag that prints the plan but does not write the output file.
  3. Re-run script and tests.

Break it (required) — Core

  1. Add two files that would rename to the same target (e.g. A.TXT and a.txt with the lower rule) -- does detect_conflicts() catch it?
  2. Add an empty filename (blank line) -- does simulate_rename() raise ValueError?
  3. Use an unknown rule name like --rule banana -- does argparse reject it or does the code crash?

Fix it (required) — Core

  1. Ensure detect_conflicts() identifies all files that would collide after renaming.
  2. Handle blank lines in the input by skipping them in simulate_batch().
  3. Add a test for the conflict-detection case.

Checkpoint: All modifications done, tests still pass. Good time to review your changes.

Explain it (teach-back)

  1. Why is this a "simulator" and not an actual renamer? What safety benefit does simulation provide?
  2. Why does RULES store functions as dict values instead of using if/elif?
  3. What does re.sub(r"^\d+[\-_ ]*", "", stem) do in apply_rule_strip_numbers()?
  4. Where would batch rename simulation appear in real software (file managers, migration scripts, DevOps tools)?

Mastery check

You can move on when you can: - run baseline without docs, - explain one core function line-by-line, - break and recover in one session, - keep tests passing after your change.

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