TheAlgorithms/Python · error · ValueError

You cannot supply more or less than 2 values

Error message

You cannot supply more or less than 2 values

What it means

Thrown by carrier_concentration() in electronics/carrier_concentration.py when the number of zeros among (electron_conc, hole_conc, intrinsic_conc) is not exactly 1. The function solves the mass-action law n*p = ni^2 for the single unknown, which the caller signals by passing 0 for that argument; supplying zero for none or for more than one argument is ambiguous.

Source

Thrown at electronics/carrier_concentration.py:44

    >>> carrier_concentration(electron_conc=1000, hole_conc=400, intrinsic_conc=1200)
    Traceback (most recent call last):
        ...
    ValueError: You cannot supply more or less than 2 values
    >>> carrier_concentration(electron_conc=-1000, hole_conc=0, intrinsic_conc=1200)
    Traceback (most recent call last):
        ...
    ValueError: Electron concentration cannot be negative in a semiconductor
    >>> carrier_concentration(electron_conc=0, hole_conc=-400, intrinsic_conc=1200)
    Traceback (most recent call last):
        ...
    ValueError: Hole concentration cannot be negative in a semiconductor
    >>> carrier_concentration(electron_conc=0, hole_conc=400, intrinsic_conc=-1200)
    Traceback (most recent call last):
        ...
    ValueError: Intrinsic concentration cannot be negative in a semiconductor
    """
    if (electron_conc, hole_conc, intrinsic_conc).count(0) != 1:
        raise ValueError("You cannot supply more or less than 2 values")
    elif electron_conc < 0:
        raise ValueError("Electron concentration cannot be negative in a semiconductor")
    elif hole_conc < 0:
        raise ValueError("Hole concentration cannot be negative in a semiconductor")
    elif intrinsic_conc < 0:
        raise ValueError(
            "Intrinsic concentration cannot be negative in a semiconductor"
        )
    elif electron_conc == 0:
        return (
            "electron_conc",
            intrinsic_conc**2 / hole_conc,
        )
    elif hole_conc == 0:
        return (
            "hole_conc",
            intrinsic_conc**2 / electron_conc,
        )

View on GitHub (pinned to f5988cc097)

Solutions

1. Pass exactly one argument as 0 — the one you want the function to compute — and real positive values for the other two.
2. If you genuinely meant a physical zero concentration, this API cannot model it; compute the mass-action result yourself instead.
3. Double-check argument order/keywords; positional mix-ups frequently leave all three non-zero.

Example fix

# before
carrier_concentration(electron_conc=100, hole_conc=200, intrinsic_conc=1200)  # no unknown

# after
carrier_concentration(electron_conc=0, hole_conc=200, intrinsic_conc=1200)
# -> ('electron_conc', 7200.0)

args = (electron_conc, hole_conc, intrinsic_conc)
if args.count(0) != 1:
    raise ValueError("pass exactly one 0 as the unknown")
name, value = carrier_concentration(*args)

When it happens

Trigger: carrier_concentration(electron_conc=0, hole_conc=0, intrinsic_conc=1200) (two zeros), or carrier_concentration(electron_conc=100, hole_conc=200, intrinsic_conc=1200) (no zero). Note that 0 here means 'unknown', not a physical zero.

Common situations: Assuming 0 is a legitimate physical concentration (doped semiconductor with no holes); migrating from an API where all three arguments were required and computed; passing None-coalesced defaults of 0.

Related errors

• Capacitor at index {index} has a negative or zero value!
• Electron concentration cannot be negative in a semiconductor
• Hole concentration cannot be negative in a semiconductor
• Intrinsic concentration cannot be negative in a semiconducto
• Source voltage must be positive.

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/d5543b4d349eeb4e. Report an issue: GitHub.