{"record":{"id":"598461c3780eca4a","repo":"TheAlgorithms/Python","slug":"type-of-band-is-not-valid-for-a-total-number-of","errorCode":null,"errorMessage":"{type_of_band} is not valid for a {total_number_of_bands} band resistor","messagePattern":"(.+?) is not valid for a (.+?) band resistor","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"electronics/resistor_color_code.py","lineNumber":256,"sourceCode":"    ValueError: sign is not valid for a 3 band resistor\n\n    >>> get_band_type_count(3,'tolerance')\n    Traceback (most recent call last):\n      ...\n    ValueError: tolerance is not valid for a 3 band resistor\n\n    >>> get_band_type_count(5,'temp_coeffecient')\n    Traceback (most recent call last):\n      ...\n    ValueError: temp_coeffecient is not valid for a 5 band resistor\n\n    \"\"\"\n    if total_number_of_bands not in band_types:\n        msg = f\"{total_number_of_bands} is not a valid number of bands\"\n        raise ValueError(msg)\n    if type_of_band not in band_types[total_number_of_bands]:\n        msg = f\"{type_of_band} is not valid for a {total_number_of_bands} band resistor\"\n        raise ValueError(msg)\n    return band_types[total_number_of_bands][type_of_band]\n\n\ndef check_validity(number_of_bands: int, colors: list) -> bool:\n    \"\"\"\n    Function checks if the input provided is valid or not.\n    Function takes number_of_bands and colors as input and returns\n    True if it is valid\n\n    >>> check_validity(3, [\"Black\",\"Blue\",\"Orange\"])\n    True\n\n    >>> check_validity(4, [\"Black\",\"Blue\",\"Orange\"])\n    Traceback (most recent call last):\n      ...\n    ValueError: Expecting 4 colors, provided 3 colors\n\n    >>> check_validity(3, [\"Cyan\",\"Red\",\"Yellow\"])","sourceCodeStart":238,"sourceCodeEnd":274,"githubUrl":"https://github.com/TheAlgorithms/Python/blob/f5988cc09713315817df6a7e327e258013a94440/electronics/resistor_color_code.py#L238-L274","documentation":"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.","triggerScenarios":"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.","commonSituations":"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.","solutions":["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').","Only request 'temp_coeffecient' when total_number_of_bands == 6; 3/4/5-band resistors have no temperature-coefficient band.","If composing calls dynamically, guard with `type_of_band in band_types.get(total_number_of_bands, {})` before calling.","Wrap the call in try/except ValueError to surface a friendly message to end users of your own tool."],"exampleFix":"# before\nn = get_band_type_count(5, 'temp_coeffecient')  # ValueError\n\n# after\nn = get_band_type_count(6, 'temp_coeffecient')  # ok: 6-band resistors have a temp coeff band","handlingStrategy":"validation","validationCode":"from electronics.resistor_color_code import band_types\n\ndef valid_band_type(bands: int, band_type: str) -> bool:\n    return bands in band_types and band_type in band_types[bands]","typeGuard":"def is_supported_band_request(bands: int, band_type: str) -> bool:\n    \"\"\"True when get_band_type_count(bands, band_type) will not raise.\"\"\"\n    return isinstance(bands, int) and bands in band_types and band_type in band_types[bands]","tryCatchPattern":"try:\n    count = get_band_type_count(bands, band_type)\nexcept ValueError as exc:\n    raise UserInputError(f\"Unsupported band configuration: {exc}\") from exc","preventionTips":["Keep band-type strings in module-level constants instead of inline literals.","Request 'temp_coeffecient' only when bands == 6.","Pin and read the band_types dict from the installed version rather than assuming its keys."],"tags":["electronics","resistor","validation","valueerror"],"backgroundTag":null,"analyzedSha":"f5988cc09713315817df6a7e327e258013a94440","analyzedAt":"2026-08-14T17:30:07.041Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}