TheAlgorithms/Python · error · ValueError

Inductance cannot be negative

Error message

Inductance cannot be negative

What it means

Thrown by ind_reactance() when the inductance argument is negative. After the exactly-one-zero check passes, the function rejects negative physical quantities; inductance in henries cannot be negative, and the guard prevents computing meaningless reactance/frequency results from a bad magnitude.

Source

Thrown at electronics/ind_reactance.py:51

    Traceback (most recent call last):
        ...
    ValueError: Inductive reactance cannot be negative

    >>> ind_reactance(0, 10e3, 50)
    {'inductance': 0.0007957747154594767}

    >>> ind_reactance(35e-3, 0, 50)
    {'frequency': 227.36420441699332}

    >>> ind_reactance(35e-6, 1e3, 0)
    {'reactance': 0.2199114857512855}

    """

    if (inductance, frequency, reactance).count(0) != 1:
        raise ValueError("One and only one argument must be 0")
    if inductance < 0:
        raise ValueError("Inductance cannot be negative")
    if frequency < 0:
        raise ValueError("Frequency cannot be negative")
    if reactance < 0:
        raise ValueError("Inductive reactance cannot be negative")
    if inductance == 0:
        return {"inductance": reactance / (2 * pi * frequency)}
    elif frequency == 0:
        return {"frequency": reactance / (2 * pi * inductance)}
    elif reactance == 0:
        return {"reactance": 2 * pi * frequency * inductance}
    else:
        raise ValueError("Exactly one argument must be 0")


if __name__ == "__main__":
    import doctest

    doctest.testmod()

View on GitHub (pinned to f5988cc097)

Solutions

1. Pass a non-negative inductance in henries (e.g. 35e-3 for 35 mH).
2. Use abs() at the call site only if the sign is known to be spurious direction metadata.
3. Trace and fix the upstream computation if a legitimately positive quantity arrives negative.

Example fix

# before
ind_reactance(-35e-3, 1e3, 0)  # ValueError: Inductance cannot be negative

# after
ind_reactance(abs(-35e-3), 1e3, 0)  # {'reactance': 0.2199114857512855}

if inductance < 0:
    raise ValueError('inductance must be >= 0')

def valid_inductance(l: float) -> bool:
    return l >= 0

try:
    out = ind_reactance(l, f, x)
except ValueError as exc:
    if 'Inductance cannot be negative' in str(exc):
        out = ind_reactance(abs(l), f, x)  # only if sign is known-spurious
    else:
        raise

When it happens

Trigger: ind_reactance(-35e-3, 1e3, 0) or ind_reactance(-0.01, 0, 50) — any call where inductance < 0 and exactly one argument is 0.

Common situations: Sign errors in unit conversions (mH to H scaling with a negative factor); raw instrument values where a minus sign indicates direction being passed through; upstream arithmetic producing a negative intermediate.

Related errors

• One and only one argument must be 0
• Frequency cannot be negative
• Inductive reactance cannot be negative
• Power cannot be negative in any electrical/electronics syste
• One and only one argument must be 0

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/bcb0fa49a2a0d0b6. Report an issue: GitHub.