Finance & Accounting

Representing money in code

Always store money as integer cents (or smallest currency unit), never as floats.

# BAD — float arithmetic is unpredictable
price = 1.10 + 2.20  # 3.3000000000000003

# GOOD — integers in cents
price_cents = 110 + 220  # 330

# Display
def format_usd(cents: int) -> str:
    return f"${cents / 100:,.2f}"

In PostgreSQL: NUMERIC(12, 0) for cents, NUMERIC(14, 2) if you need fractional cents (e.g., per-unit pricing).