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 electric_conductivity() in electronics/electric_conductivity.py when the number of zeros among (conductivity, electron_conc, mobility) is not exactly 1. The function solves sigma = n*e*mu for the single unknown, signaled by passing 0 for that argument; supplying zero for none or several arguments is ambiguous.

Source

Thrown at electronics/electric_conductivity.py:46

    >>> electric_conductivity(conductivity=50, electron_conc=-10, mobility=0)
    Traceback (most recent call last):
        ...
    ValueError: Electron concentration cannot be negative
    >>> electric_conductivity(conductivity=50, electron_conc=0, mobility=-10)
    Traceback (most recent call last):
        ...
    ValueError: mobility cannot be negative
    >>> electric_conductivity(conductivity=50, electron_conc=0, mobility=0)
    Traceback (most recent call last):
        ...
    ValueError: You cannot supply more or less than 2 values
    >>> electric_conductivity(conductivity=50, electron_conc=200, mobility=300)
    Traceback (most recent call last):
        ...
    ValueError: You cannot supply more or less than 2 values
    """
    if (conductivity, electron_conc, mobility).count(0) != 1:
        raise ValueError("You cannot supply more or less than 2 values")
    elif conductivity < 0:
        raise ValueError("Conductivity cannot be negative")
    elif electron_conc < 0:
        raise ValueError("Electron concentration cannot be negative")
    elif mobility < 0:
        raise ValueError("mobility cannot be negative")
    elif conductivity == 0:
        return (
            "conductivity",
            mobility * electron_conc * ELECTRON_CHARGE,
        )
    elif electron_conc == 0:
        return (
            "electron_conc",
            conductivity / (mobility * ELECTRON_CHARGE),
        )
    else:
        return (

View on GitHub (pinned to f5988cc097)

Solutions

1. Pass exactly one argument as 0 (the unknown) and positive values for the other two.
2. Read the function's docstring doctests to confirm the intended calling convention before wiring calls.
3. Wrap the call with a helper that takes explicit 'solve_for' semantics if the 0-marker convention is error-prone in your codebase.

Example fix

# before
electric_conductivity(conductivity=50, electron_conc=200, mobility=300)  # no unknown

# after
electric_conductivity(conductivity=0, electron_conc=200, mobility=300)
# -> ('conductivity', ...)

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

When it happens

Trigger: electric_conductivity(conductivity=50, electron_conc=0, mobility=0) (two zeros) or electric_conductivity(conductivity=50, electron_conc=200, mobility=300) (no zero).

Common situations: Assuming all three arguments are required and passing measured values for each; None-coalescing to 0 defaults; confusion of the '0 means solve-for-this' convention shared by several functions in this electronics package.

Related errors

• You cannot supply more or less than 2 values
• Electron concentration cannot be negative in a semiconductor
• Hole concentration cannot be negative in a semiconductor
• Intrinsic concentration cannot be negative in a semiconducto
• One and only one argument must be 0

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/53dc824e1fe4c9a4. Report an issue: GitHub.