TheAlgorithms/Python · error · ValueError

Cash flows list cannot be empty

Error message

Cash flows list cannot be empty

What it means

Raised by present_value() when cash_flows is empty (falsy). Summing discounts over zero flows is defined mathematically as 0, but the library treats an empty schedule as caller error — most likely a missing or misparsed input — and rejects it before the sum() generator runs.

Source

Thrown at financial/present_value.py:32

    >>> present_value(0.13, [10, 20.70, -293, 297])
    4.69
    >>> present_value(0.07, [-109129.39, 30923.23, 15098.93, 29734,39])
    -42739.63
    >>> present_value(0.07, [109129.39, 30923.23, 15098.93, 29734,39])
    175519.15
    >>> present_value(-1, [109129.39, 30923.23, 15098.93, 29734,39])
    Traceback (most recent call last):
        ...
    ValueError: Discount rate cannot be negative
    >>> present_value(0.03, [])
    Traceback (most recent call last):
        ...
    ValueError: Cash flows list cannot be empty
    """
    if discount_rate < 0:
        raise ValueError("Discount rate cannot be negative")
    if not cash_flows:
        raise ValueError("Cash flows list cannot be empty")
    present_value = sum(
        cash_flow / ((1 + discount_rate) ** i) for i, cash_flow in enumerate(cash_flows)
    )
    return round(present_value, ndigits=2)


if __name__ == "__main__":
    import doctest

    doctest.testmod()

View on GitHub (pinned to f5988cc097)

Solutions

1. Check the flows list is non-empty before calling; investigate why it is empty.
2. Fix the upstream filter/parsing that produced zero cash flows.
3. If an empty schedule is legitimate in your domain, return 0 explicitly in your wrapper rather than calling the function.

Example fix

# before
flows = [f for f in all_flows if f.date <= cutoff]  # cutoff too early -> []
pv = present_value(0.03, flows)

# after
flows = [f for f in all_flows if f.date <= cutoff]
if not flows:
    raise ValueError('no cash flows in window')
pv = present_value(0.03, flows)

if not cash_flows:
    raise ValueError('cash flow schedule is empty')
present_value(rate, cash_flows)

def is_nonempty_numeric_flows(flows: object) -> bool:
    return isinstance(flows, list) and len(flows) > 0 and all(
        isinstance(f, (int, float)) for f in flows
    )

try:
    pv = present_value(r, flows)
except ValueError as exc:
    if 'Cash flows' in str(exc):
        pv = 0.0
    else:
        raise

When it happens

Trigger: Calling present_value(0.03, []) or with any falsy flows value (empty tuple, None). Reached only after the discount-rate check passes.

Common situations: Parsing a CSV/date-range filter that yields no rows, a typo'd schedule variable defaulting to [], or passing None for the flows argument.

Related errors

• number_of_years must be > 0
• nominal_annual_percentage_rate must be >= 0
• Discount rate cannot be negative
• Window size must be a positive integer
• Useful years cannot be less than 1

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/b95b557da0b633de. Report an issue: GitHub.