TheAlgorithms/Python · error · ValueError

{type_of_band} is not valid for a {total_number_of_bands} ba

Error message

{type_of_band} is not valid for a {total_number_of_bands} band resistor

What it means

Raised by get_band_type_count() in electronics/resistor_color_code.py when the requested band type (e.g. 'significant', 'multiplier', 'tolerance', 'temp_coeffecient') is not a key in band_types[total_number_of_bands]. The library models resistors with 3-6 bands, and each band count only supports a fixed set of band types (e.g. temperature coefficient only exists on 6-band resistors). The sibling check one line earlier rejects band counts outside 3-6 with a different message.

Source

Thrown at electronics/resistor_color_code.py:256

    ValueError: sign is not valid for a 3 band resistor

    >>> get_band_type_count(3,'tolerance')
    Traceback (most recent call last):
      ...
    ValueError: tolerance is not valid for a 3 band resistor

    >>> get_band_type_count(5,'temp_coeffecient')
    Traceback (most recent call last):
      ...
    ValueError: temp_coeffecient is not valid for a 5 band resistor

    """
    if total_number_of_bands not in band_types:
        msg = f"{total_number_of_bands} is not a valid number of bands"
        raise ValueError(msg)
    if type_of_band not in band_types[total_number_of_bands]:
        msg = f"{type_of_band} is not valid for a {total_number_of_bands} band resistor"
        raise ValueError(msg)
    return band_types[total_number_of_bands][type_of_band]


def check_validity(number_of_bands: int, colors: list) -> bool:
    """
    Function checks if the input provided is valid or not.
    Function takes number_of_bands and colors as input and returns
    True if it is valid

    >>> check_validity(3, ["Black","Blue","Orange"])
    True

    >>> check_validity(4, ["Black","Blue","Orange"])
    Traceback (most recent call last):
      ...
    ValueError: Expecting 4 colors, provided 3 colors

    >>> check_validity(3, ["Cyan","Red","Yellow"])

View on GitHub (pinned to f5988cc097)

Solutions

1. Use only the exact band-type keys defined in the band_types dict at the top of electronics/resistor_color_code.py ('significant', 'multiplier', 'tolerance', 'temp_coeffecient').
2. Only request 'temp_coeffecient' when total_number_of_bands == 6; 3/4/5-band resistors have no temperature-coefficient band.
3. If composing calls dynamically, guard with `type_of_band in band_types.get(total_number_of_bands, {})` before calling.
4. Wrap the call in try/except ValueError to surface a friendly message to end users of your own tool.

Example fix

# before
n = get_band_type_count(5, 'temp_coeffecient')  # ValueError

# after
n = get_band_type_count(6, 'temp_coeffecient')  # ok: 6-band resistors have a temp coeff band

from electronics.resistor_color_code import band_types

def valid_band_type(bands: int, band_type: str) -> bool:
    return bands in band_types and band_type in band_types[bands]

def is_supported_band_request(bands: int, band_type: str) -> bool:
    """True when get_band_type_count(bands, band_type) will not raise."""
    return isinstance(bands, int) and bands in band_types and band_type in band_types[bands]

try:
    count = get_band_type_count(bands, band_type)
except ValueError as exc:
    raise UserInputError(f"Unsupported band configuration: {exc}") from exc

When it happens

Trigger: Calling get_band_type_count(5, 'temp_coeffecient') (temperature coefficient is only defined for 6-band resistors), or misspelling a type like 'significant figures' or 'tolerence' instead of the exact keys used in the band_types dict.

Common situations: Dynamically computing how many significant-figure bands a resistor has from user input; iterating band types per band count and assuming all types exist for every count; typos in the type_of_band string after a refactor.

Related errors

• {color} is not a valid color for significant figure bands
• {total_number_of_bands} is not a valid number of bands
• Power cannot be negative in any electrical/electronics syste
• One and only one argument must be 0
• One and only one argument must be 0

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/598461c3780eca4a. Report an issue: GitHub.