Migrate data transform CLI to Python

.github/workflows/ci.yml

@@ -10,13 +10,17 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [20, 22]
+        python-version: ["3.11", "3.12"]
     steps:
       - uses: actions/checkout@v4
-      - name: Use Node.js ${{ matrix.node-version }}
-        uses: actions/setup-node@v4
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
         with:
-          node-version: ${{ matrix.node-version }}
-          cache: npm
-      - run: npm ci
-      - run: npm test
+          python-version: ${{ matrix.python-version }}
+          cache: pip
+      - name: Install package and test deps
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev]"
+      - name: Run tests
+        run: pytest

.gitignore

@@ -1,11 +1,19 @@
-node_modules/
-npm-debug.log*
-yarn-debug.log*
-yarn-error.log*
-.DS_Store
-*.tgz
-coverage/
-.nyc_output/
+__pycache__/
+*.py[cod]
+*$py.class
+*.egg-info/
+.eggs/
 dist/
+build/
+.pytest_cache/
+.mypy_cache/
+.ruff_cache/
+.coverage
+htmlcov/
+.venv/
+venv/
+.env
+.DS_Store
 .idea/
 .vscode/
+*.egg

CONTRIBUTING.md

@@ -2,20 +2,20 @@
 
 ## Setup
 
-- Use Node 20 or newer
-- Install dependencies with the package manager
-- Run the test script from package.json
+- Use Python 3.11 or newer
+- Install with `pip install -e ".[dev]"`
+- Run tests with `pytest`
 
 ## Guidelines
 
-- Keep the CLI ESM-only (type module).
+- Keep the public CLI entry as the `data-transform` console script.
 - Prefer small, focused changes with tests for round-trips and edge cases.
 - Do not add company names or personal contacts in committed files.
-- Match existing style: errors on stderr, exit code 1 on failure, UTF-8 I/O.
+- Match existing style: errors on stderr as `error: …`, exit code 1 on failure, UTF-8 I/O.
 
 ## Pull requests
 
 1. Fork and branch from main.
-2. Add or update tests under test/.
-3. Ensure the test script passes.
+2. Add or update tests under `tests/`.
+3. Ensure `pytest` passes.
 4. Open a PR with a short summary of the change and why.

README.md

@@ -1,24 +1,19 @@
 # data-transform-cli
 
-Node.js ESM CLI for **YAML ↔ JSON ↔ CSV** transforms. Built for shell pipelines and local scripts.
+Python CLI for **YAML ↔ JSON ↔ CSV** transforms. Built for shell pipelines and local scripts.
 Streaming-friendly where practical (stdin/stdout; full documents buffered for parse safety).
 
-Requires **Node.js 20+**.
+Requires **Python 3.11+**.
 
 ## Install
 
 ```bash
-npm install -g .
-# or run without installing:
-npx --yes . to-json ./data.yaml
+pip install -e .
+# or with test extras:
+pip install -e ".[dev]"
 ```
 
-From a clone of this repo:
-
-```bash
-npm install
-npm link   # optional: exposes data-transform on your PATH
-```
+After install, the `data-transform` console script is on your `PATH`.
 
 ## Commands
 
@@ -63,46 +58,26 @@ printf "a: 1\n" | data-transform to-json -f yaml
 
 ### Library use
 
-```js
-import { convert, parse, serialize } from "data-transform-cli";
+```python
+from data_transform import convert, parse, serialize
 
-const yaml = convert("{\"a\":1}", "json", "yaml");
-const data = parse("id,name\n1,x\n", "csv");
-const json = serialize(data, "json", { pretty: true });
+yaml_text = convert('{"a":1}', "json", "yaml")
+data = parse("id,name\n1,x\n", "csv")
+json_text = serialize(data, "json", pretty=True)
 ```
 
 ## CSV notes
 
-CSV support is intentionally small and robust (RFC 4180-ish): quoted fields, escaped quotes (`""`), and newlines inside quotes. Object arrays use a header row; all cell values are strings when parsed from CSV.
+CSV support is intentionally small and robust (RFC 4180-ish) via the Python standard library `csv` module: quoted fields, escaped quotes (`""`), and newlines inside quotes. Object arrays use a header row; all cell values are strings when parsed from CSV.
 
 ## Development
 
 ```bash
-npm install
-npm test
+pip install -e ".[dev]"
+pytest
 ```
 
-Tests use Node built-in `node:test` runner with fixtures under `test/fixtures/` for JSON/YAML/CSV round-trips and CLI smoke checks.
-
-## Extending with coding agents
-
-### GitHub Copilot
-
-- Open this repo in VS Code / JetBrains with Copilot enabled.
-- Prefer asking Copilot to follow existing modules (`src/convert.js`, `src/csv.js`) and to add `node:test` cases beside fixtures.
-- Optional: add workspace guidance under `.github/copilot-instructions.md`.
-
-### Claude Code
-
-- From the repo root, open the folder in Claude Code (or its CLI).
-- Point it at `CONTRIBUTING.md` and ask for a failing test first, then implementation.
-- Keep changes ESM-compatible and avoid adding heavy CSV libraries unless needed.
-
-### OpenAI Codex
-
-- Open the project in Codex with this directory as the workspace.
-- Ask for command-level changes (`to-json`, `to-csv`, ...) and matching CLI tests in `test/cli.test.js`.
-- Remind the agent: no company names, no personal contacts, no generator authorship comments in committed files.
+Tests use **pytest** with fixtures under `tests/fixtures/` for JSON/YAML/CSV round-trips and CLI smoke checks.
 
 ## License
 

pyproject.toml

@@ -0,0 +1,35 @@
+[build-system]
+requires = ["setuptools>=68", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "data-transform-cli"
+version = "0.1.0"
+description = "CLI for YAML ↔ JSON ↔ CSV transforms for pipelines and shell use"
+readme = "README.md"
+license = { text = "MIT" }
+requires-python = ">=3.11"
+authors = [{ name = "rmkr-dev" }]
+keywords = ["cli", "yaml", "json", "csv", "transform", "pipeline"]
+dependencies = [
+  "click>=8.1",
+  "PyYAML>=6.0",
+]
+
+[project.optional-dependencies]
+dev = ["pytest>=8.0"]
+
+[project.scripts]
+data-transform = "data_transform.cli:main"
+
+[project.urls]
+Homepage = "https://github.com/rmkr-dev/data-transform-cli"
+Repository = "https://github.com/rmkr-dev/data-transform-cli"
+Issues = "https://github.com/rmkr-dev/data-transform-cli/issues"
+
+[tool.setuptools.packages.find]
+where = ["src"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+pythonpath = ["src"]