The Life Starter
Sign up
All courses/Digital

Course 269 · Digital course 32

Build a Python File-Processing Tool

Build a local command-line converter that validates fictional attendance CSV, writes JSON to a chosen output and reports rejected rows without altering input. Work from supplied original examples and check changed cases.

Before you start

Complete or review Programming with Python before starting.

Programming with Python See everything you’ll need

Free download · Original practice data · No external account required. Download the starter pack

What you’ll leave with

A local command-line converter that validates fictional attendance CSV, writes JSON to a chosen output and reports rejected rows without altering input.

Start course Start without an account. Sign in to save lesson progress across devices.

Your project

Start with the practice files. Build your project one lesson at a time.

Practice files are free without an account. Sign in to save your project record in My Proof: a description, checklist, and optional work link. Keep the original files in your own app or notebook; saving a project record does not upload them.

  1. Get your materialsDownload practice filesSupplied practice cases, a blank working record, complete lesson instructions, and annotated worked examples.
  2. Make your projectView the project checklist Work in your own notebook, document, or software. Use the supplied practice examples when you prefer.
  3. Keep a private recordSave a project record Sign in to save a description and checklist, then return to update them.
Course handbook

Know the route before you begin.

Here’s what you’ll need and what you’ll make. You can return to this guide during any lesson.

Who this is for

Learners ages 14+ and adults ready for the named prerequisite; no employment or private records required.

Prepare before lesson one
  • Complete or review Programming with Python before starting.
  • Use a local text editor and a free Python 3.10+ interpreter for Python files, or a current browser for HTML files. Supplied code uses no paid services or external packages.
  • Create a fresh practice folder and use only the supplied fictional inputs. A paper trace is labeled a trace, not an executed test.
Your final project

Finish with proof you can use.

A local command-line converter that validates fictional attendance CSV, writes JSON to a chosen output and reports rejected rows without altering input.

Save a project record in My Proof
See project checklist and review criteria

Keep your working files in your own notebook or software. Save a private description, checklist, and work link in My Proof.

What to include

  • A converter contract with two accepted and two rejected records.
  • A CSV-to-typed-record trace with invalid-value evidence.
  • A failure report distinguishing rejected rows from failed runs.
  • A checked JSON output with 2 accepted and 2 rejected entries.
  • A reusable command contract and a missing-argument test.
  • A repeatable local CSV converter with failure and preservation evidence.

Review and revise

Use these criteria to check your work and choose what to improve.

  • The implementation or declared simulation follows the supplied contract and retains inspectable original inputs.
  • Normal, boundary and rejected cases are recorded with expected versus observed results.
  • The changed case has a correct explanation and does not rely on hidden state.
  • The project includes source, outputs, instructions and honest tool, privacy and verification limits.
Three ideas to help you along the way
Three useful ideas

The rules behind the steps.

01

State the contract

Name inputs, permitted states and observable outputs before editing the implementation.

02

Preserve the evidence

Keep the actual source, changed input and expected/observed record so someone can repeat the work.

03

Test the boundary

Check a rejection or changed case and distinguish local practice from real service or native-tool behavior.

What do these words mean?
Key words

Key terms worth knowing.

Schema
The declared field names, types and constraints.
Serialization
Encoding structured values as file text.
Exit code
A process status where zero normally means success.
Positional argument
A command value identified by its position.
Your route

6 lessons.
One useful project.

Work in order the first time. Each lesson makes something the next lesson can use.

  1. 1
    Up next

    Define the command and file contract

    Use the supplied case to define the command and file contract and retain an inspectable converter contract with two accepted and two rejected records.

  2. 2
    19 min

    Read CSV with explicit types

    Use the supplied case to read csv with explicit types and retain an inspectable CSV-to-typed-record trace with invalid-value evidence.

  3. 3
    22 min

    Report invalid records and file errors

    Use the supplied case to report invalid records and file errors and retain an inspectable failure report distinguishing rejected rows from failed runs.

  4. 4
    19 min

    Write a separate JSON output

    Use the supplied case to write a separate json output and retain an inspectable checked JSON output with 2 accepted and 2 rejected entries.

  5. 5
    19 min

    Add command-line arguments

    Use the supplied case to add command-line arguments and retain an inspectable reusable command contract and a missing-argument test.

  6. 6
    26 min

    Test repeatable and failed runs

    Use the supplied case to test repeatable and failed runs and retain an inspectable repeatable local CSV converter with failure and preservation evidence.

Use the tools

Tools to help you practice.

See all tools
ZIP · practice files

Build a Python File-Processing Tool practice files

Supplied practice cases, a blank working record, complete lesson instructions, and annotated worked examples.

Text worksheet

Your course project worksheet

A downloadable text worksheet with each lesson’s working output, space for your answers, and the shared final-project checklist. Save your own copy.

Source transparency

Sources and further study.

Explore the references behind the lessons and take your learning further. Source notes explain access and reuse.

docs.python.org — csv.html
Source & access notes · checked 2026-10-01

Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.

Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.

Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.

docs.python.org — argparse.html
Source & access notes · checked 2026-10-01

Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.

Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.

Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.

docs.python.org — pathlib.html
Source & access notes · checked 2026-10-01

Relevant documented module/API behavior inspected during expansion authoring; actual execution evidence is recorded separately. No grant eligibility is established.

Access: Official page retrieved with the web reader on 2026-10-01. Documentation reading does not certify execution in every native tool or browser.

Reuse: Original local practice files, fictional data, worked examples and questions. Concepts paraphrased and linked; source exercises are not copied.

Ready when you are

Start with the first useful move.

You’ll always know what to do, what to make, and where to go next.

Start lesson one