TheAlgorithms/Python · error · ValueError

Purchase value cannot be less than zero

Error message

Purchase value cannot be less than zero

What it means

Raised by straight_line_depreciation() when purchase_value is numeric but negative (ValueError). A negative purchase price makes depreciable_cost negative and produces a nonsense schedule of negative expenses, so the function rejects it after type checks. Zero is allowed.

Source

Thrown at financial/straight_line_depreciation.py:68

    [30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0]
    >>> straight_line_depreciation(1, 4985, 100)
    [4885.0]
    """

    if not isinstance(useful_years, int):
        raise TypeError("Useful years must be an integer")

    if useful_years < 1:
        raise ValueError("Useful years cannot be less than 1")

    if not isinstance(purchase_value, (float, int)):
        raise TypeError("Purchase value must be numeric")

    if not isinstance(residual_value, (float, int)):
        raise TypeError("Residual value must be numeric")

    if purchase_value < 0.0:
        raise ValueError("Purchase value cannot be less than zero")

    if purchase_value < residual_value:
        raise ValueError("Purchase value cannot be less than residual value")

    # Calculate annual depreciation expense
    depreciable_cost = purchase_value - residual_value
    annual_depreciation_expense = depreciable_cost / useful_years

    # List of annual depreciation expenses
    list_of_depreciation_expenses = []
    accumulated_depreciation_expense = 0.0
    for period in range(useful_years):
        if period != useful_years - 1:
            accumulated_depreciation_expense += annual_depreciation_expense
            list_of_depreciation_expenses.append(annual_depreciation_expense)
        else:
            depreciation_expense_in_end_year = (
                depreciable_cost - accumulated_depreciation_expense

View on GitHub (pinned to f5988cc097)

Solutions

1. Pass purchase_value >= 0.
2. Investigate the source of the negative basis — usually an upstream double-entry error worth surfacing, not silently fixing.
3. If reversals are legitimate in your pipeline, handle them before depreciation, not through this API.

Example fix

# before
straight_line_depreciation(5, net_cost_basis, 50.0)  # -1250.0 after reversals

# after
if net_cost_basis < 0:
    raise ValueError(f'negative cost basis from reversals: {net_cost_basis}')
straight_line_depreciation(5, net_cost_basis, 50.0)

if purchase_value < 0:
    raise ValueError(f'purchase value cannot be negative: {purchase_value}')
straight_line_depreciation(5, purchase_value, residual)

try:
    sched = straight_line_depreciation(y, p, r)
except ValueError as exc:
    if 'less than zero' in str(exc):
        flag_for_review(p)
        raise
    raise

When it happens

Trigger: Calling straight_line_depreciation(5, -1250.0, 50.0) or passing a credit-note-adjusted cost basis that went below zero.

Common situations: Accounting systems storing reversals/refunds as negatives, currency-adjusted bases that underflow to negative, or sign-convention mistakes when importing GL data.

Related errors

• number_of_years must be > 0
• nominal_annual_percentage_rate must be >= 0
• Discount rate cannot be negative
• Cash flows list cannot be empty
• Window size must be a positive integer

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/10659e1197025752. Report an issue: GitHub.