Materials for Antigravity CLI (#786)

* Materials for Antigravity CLI

* Add a test fixture to reproduce the zerodivision error

Author: bzaczynski

antigravity-cli/README.md

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+# How to Use Google's Antigravity CLI for AI Code Assistance
+
+This folder contains code associated with the Real Python tutorial [How to Use Google's Antigravity CLI for AI Code Assistance](https://realpython.com/antigravity-cli/).

antigravity-cli/expense-report/.gitignore

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+# Created by https://www.toptal.com/developers/gitignore/api/python,pycharm+all,visualstudiocode
+# Edit at https://www.toptal.com/developers/gitignore?templates=python,pycharm+all,visualstudiocode
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antigravity-cli/expense-report/AGENTS.md

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+# Project conventions
+
+This is a small command-line tool that reads a CSV of personal transactions and
+prints a per-category expense summary.
+
+## Money
+
+- Represent every monetary amount with `decimal.Decimal`, never `float`.
+- Quantize money to exactly two decimal places before displaying it.
+
+## Style
+
+- Keep functions small and single-purpose.
+- Standard library only. No third-party dependencies.

antigravity-cli/expense-report/README.md

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+# expense-report
+
+A tiny command-line tool that summarizes personal transactions from a CSV file.
+
+```console
+$ python cli.py transactions.csv
+```

antigravity-cli/expense-report/cli.py

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+"""Command-line entry point for the expense reporter."""
+
+import sys
+
+from transactions import report
+
+
+def main():
+    path = sys.argv[1] if len(sys.argv) > 1 else "transactions.csv"
+    print(report(path))
+
+
+if __name__ == "__main__":
+    main()

antigravity-cli/expense-report/transactions.csv

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+date,category,description,amount
+2026-01-03,Groceries,Corner store,12.10
+2026-01-05,Transport,Bus pass,40.00
+2026-01-09,Groceries,Farmers market,8.20
+2026-01-12,Dining,Coffee,4.10
+2026-01-15,Dining,Lunch,11.20
+2026-01-18,Groceries,Supermarket,53.40
+2026-01-21,Transport,Taxi,18.75
+2026-01-24,Dining,Dinner,29.30
+2026-01-27,Utilities,Electricity,64.30
+2026-01-29,Groceries,Bakery,3.10

antigravity-cli/expense-report/transactions.py

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+"""Summarize a CSV of personal transactions by category."""
+
+import csv
+
+
+def report(path):
+    rows = []
+    with open(path, newline="") as f:
+        reader = csv.DictReader(f)
+        for row in reader:
+            rows.append(row)
+
+    totals = {}
+    count = 0
+    grand_total = 0.0
+    for row in rows:
+        category = row["category"]
+        amount = float(row["amount"])
+        if category not in totals:
+            totals[category] = 0.0
+        totals[category] += amount
+        grand_total += amount
+        count += 1
+
+    lines = []
+    lines.append("Expense report")
+    lines.append("=" * 32)
+    for category in sorted(totals, key=lambda c: totals[c], reverse=True):
+        share = totals[category] / grand_total * 100
+        lines.append(f"{category:<14}{totals[category]:>10} ({share:.1f}%)")
+    lines.append("-" * 32)
+    lines.append(f"{'TOTAL':<14}{grand_total:>10}")
+    lines.append(f"{count} transactions")
+    return "\n".join(lines)

antigravity-cli/expense-report/transactions_zero.csv

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+date,category,amount
+2026-01-05,Refunds,-50.00
+2026-01-06,Purchases,50.00