PET - Personal Expense Tracker (Go)

Go port of the Python PET CLI. Stores data in expenses.csv, in the same format the Python version uses — CSV files are interchangeable between the two.

Features

• Add expenses (amount, description, category, optional date)
• List expenses (with optional filters: month/year/category)
• View summary (total, average, min/max, category breakdown)
• Delete expenses by index

Build

go build -o pet .

No external dependencies — standard library only, same as the Python version's empty requirements.txt.

Usage

./pet add 420 "Lunch" -c Food
./pet list
./pet list --show-index
./pet list --month 1 --year 2026
./pet summary
./pet summary --month 12
./pet delete 3
./pet --help
./pet add -h

Notes on this port

• Flags work in any position, e.g. pet add 420 "Lunch" -c Food — Go's flag package normally requires flags before positional arguments; this is worked around with a small pre-parse step so the CLI syntax matches the Python version exactly.
• CSV format is byte-compatible: expenses.csv written by either version is interchangeable (same headers, same \r\n line endings from Python's csv module default, same %.2f amount formatting).
• More defensive parsing than the original: a malformed row (bad amount, bad date) is skipped rather than aborting the entire load, and -d/--date on add is validated up front instead of failing silently later.
• Fixed a formatting inconsistency: in the Python version, deleting an expense rewrites the CSV without reapplying .2f formatting, so amounts can drift (e.g. 420.00 becomes 420.0). The Go version formats consistently on every write.
• Preserved as-is from the original: when --show-index is combined with --month/--category, the index shown is the position within the filtered list, not the full dataset — so it won't line up with delete unless you're looking at the unfiltered list. This was true in the Python version too.