Debug Report

Stack: Python 3.11, standard library only | Issues fixed: 3 of up to 3

Summary

The report script had three problems. It read dates in day/month/year order, but your file stores them as year-month-day. It also tried to add to each customer's total before that total existed, and it was adding text instead of numbers. Finally, the loop skipped the first order in the file. I fixed all three with small, marked changes, kept both function names, and used only the standard library.

Issues & Root Causes

Issue 1: Date format doesn't match the CSV

• Symptom: ValueError: time data '2024-03-02' does not match format '%d/%m/%Y'
• Where: report.py, load_orders(), line 14
• Root cause: The format '%d/%m/%Y' expects dates like 02/03/2024. Your CSV uses ISO dates like 2024-03-02, which need '%Y-%m-%d'. The error names 2024-03-02 (row 2) rather than 2024-03-01 (row 1), which points to Issue 3: the first row was never read.
• Fix: I changed the format string to '%Y-%m-%d' so it matches the file.
• Confidence: High. The traceback and the sample data match exactly.

Issue 2: Totals crash because there's no starting value, and amounts are text

• Symptom: KeyError: 'Acme Co' in totals_by_customer
• Where: report.py, totals_by_customer(), line 21. Also load_orders(), line 13
• Root cause: totals[o['customer']] += ... reads the current total before adding to it. The first time a customer appears, there's no entry yet, so Python raises KeyError. There is a second problem in the same calculation: csv always returns values as text. So 'amount' was the string '120.50', not a number. Even with the KeyError fixed, adding text to a number would crash next with a TypeError, and :.2f can't format text either.
• Fix: I convert each amount with float(row['Amount']) when loading. I also start each customer at 0 with totals.get(o['customer'], 0) + o['amount']. I counted these two changes as one issue because both are needed before the totals can be added up at all.
• Confidence: High. Both are standard Python behavior.

Issue 3: The first order is skipped

• Symptom: The totals looked low.
• Where: report.py, load_orders(), line 9
• Root cause: csv.DictReader already uses the header line (Customer,Amount,Date) for the column names. So rows[0] is your first real order (Acme Co, 120.50), not the header. Starting the loop at range(1, ...) threw that order away. That's why Acme Co would have shown $30.00 instead of $150.50.
• Fix: I changed the loop to range(len(rows)) so it starts at index 0.
• Confidence: High. This is how DictReader is documented to work, and the clue in Issue 1's error message confirms it.

Fixed Files

report.py

import csv
from datetime import datetime

def load_orders(path):
    orders = []
    with open(path) as f:
        reader = csv.DictReader(f)
        rows = list(reader)
        for i in range(len(rows)):  # FIX 3: start at 0; DictReader already consumed the header line
            row = rows[i]
            orders.append({
                'customer': row['Customer'],
                'amount': float(row['Amount']),  # FIX 2: CSV values are text; convert to a number
                'date': datetime.strptime(row['Date'], '%Y-%m-%d')  # FIX 1: CSV dates are YYYY-MM-DD
            })
    return orders

def totals_by_customer(orders):
    totals = {}
    for o in orders:
        totals[o['customer']] = totals.get(o['customer'], 0) + o['amount']  # FIX 2: start each customer at 0
    return totals

if __name__ == '__main__':
    orders = load_orders('orders.csv')
    for name, total in totals_by_customer(orders).items():
        print(f'{name}: ${total:.2f}')

Files reviewed, unchanged: orders.csv

Change Log

How to Verify

1. Put report.py and orders.csv in the same folder and run:

   python report.py
   

   With the 4 sample lines you pasted (header plus 3 orders), you should see:

   Acme Co: $150.50
   Bolt LLC: $75.00
   

   • No ValueError means Issue 1 is fixed.
   • No KeyError means Issue 2 is fixed.
   • Acme Co at $150.50 rather than $30.00 means Issue 3 is fixed.
2. Optional automated tests. Save the file below as test_report.py in the same folder and run python -m unittest test_report -v. All three tests should pass.

import os
import tempfile
import unittest
from datetime import datetime

from report import load_orders, totals_by_customer

SAMPLE = (
    "Customer,Amount,Date\n"
    "Acme Co,120.50,2024-03-01\n"
    "Bolt LLC,75.00,2024-03-02\n"
    "Acme Co,30.00,2024-03-05\n"
)

class ReportTests(unittest.TestCase):
    def setUp(self):
        fd, self.path = tempfile.mkstemp(suffix=".csv")
        with os.fdopen(fd, "w") as f:
            f.write(SAMPLE)

    def tearDown(self):
        os.remove(self.path)

    def test_issue1_iso_dates_parse(self):
        orders = load_orders(self.path)
        self.assertEqual(orders[0]['date'], datetime(2024, 3, 1))

    def test_issue2_totals_are_numbers_and_no_keyerror(self):
        totals = totals_by_customer(load_orders(self.path))
        self.assertAlmostEqual(totals['Acme Co'], 150.50)
        self.assertAlmostEqual(totals['Bolt LLC'], 75.00)

    def test_issue3_first_row_not_skipped(self):
        orders = load_ord