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BeginnerPython project

Expense summary command-line tool

Turn lines of expense data into a trustworthy summary. The program reads category and amount pairs, rejects malformed entries without crashing, totals valid expenses by category and prints both a category report and the overall spend.

Skills you will practise

  • input parsing
  • dictionaries
  • functions
  • exceptions
  • sorting and formatting

Project requirements

  • Read until the input ends.
  • Accept lines in category,amount format.
  • Skip empty, malformed, negative or non-numeric amounts.
  • Print categories alphabetically with amounts to two decimal places.
  • Print the grand total and the number of rejected lines.

Build it in stages

  1. 1

    Parse one record

    Write a function that splits once at the comma, trims both fields and converts the amount to float. Return a clear success or failure result.

  2. 2

    Accumulate valid expenses

    Use a dictionary keyed by category. Add repeated categories instead of replacing their previous totals.

  3. 3

    Track rejected input

    Catch only the conversion and shape errors you expect. Count rejected lines without hiding unrelated programming mistakes.

  4. 4

    Render the report

    Move formatting into a function that sorts categories, prints fixed two-decimal amounts and ends with the overall total and rejected count.

Starter code

 Python
def parse_expense(line):
    # Return (category, amount) or None.
    pass

totals = {}
rejected = 0
# Read lines, validate them and build the report.

Open the Python playground

Expected result

For input food,12.50 / travel,8 / food,3.25 / broken, the report contains food 15.75, travel 8.00, total 23.75 and rejected 1.

Progressive hints

Hint 1

split(',', 1) prevents extra commas from silently creating too many fields.

Hint 2

Use totals.get(category, 0) when adding a repeated category.

Hint 3

Keep calculation values numeric; apply :.2f only when printing.

Solution guidance

Show the approach after you attempt the project

The maintainable design has three parts: parse one line, accumulate valid data and render the finished report. This separation makes boundary cases testable without simulating the whole program. Catch ValueError around float conversion, reject non-positive categories or negative amounts explicitly, and let unexpected exceptions surface. Dictionary accumulation preserves one source of truth, while sorting only at output time avoids coupling storage to presentation.

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