{"record":{"id":"9540276c90df58f8","repo":"TheAlgorithms/Python","slug":"total-number-of-bands-is-not-a-valid-number-of-b","errorCode":null,"errorMessage":"{total_number_of_bands} is not a valid number of bands","messagePattern":"(.+?) is not a valid number of bands","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"electronics/resistor_color_code.py","lineNumber":253,"sourceCode":"    >>> get_band_type_count(3,'sign')\n    Traceback (most recent call last):\n      ...\n    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      ...","sourceCodeStart":235,"sourceCodeEnd":271,"githubUrl":"https://github.com/TheAlgorithms/Python/blob/f5988cc09713315817df6a7e327e258013a94440/electronics/resistor_color_code.py#L235-L271","documentation":"Thrown by get_band_type_count() in electronics/resistor_color_code.py when total_number_of_bands is not a key of the band_types dict — i.e. not one of the supported band counts (3, 4, 5, 6 per the table). A separate, second ValueError ('... is not valid for a N band resistor') fires when the count is valid but the band type is not present at that count; this one covers the count itself.","triggerScenarios":"get_band_type_count(2, 'significant'); get_band_type_count(7, 'temp_coeffecient'); get_band_type_count('4', 'significant') (string key never matches int keys in band_types).","commonSituations":"Miscounting bands on a small or oddly-marked resistor; passing a string digit from parsed input instead of int; assuming arbitrary band counts are supported when only 3-6 are.","solutions":["Pass an int band count within the supported set: get_band_type_count(3, 'significant') -> 2.","Coerce parsed values: int(total_number_of_bands) before calling.","Verify the band count against the table keys (commonly band_types.keys()) or 3..6."],"exampleFix":"# before\nget_band_type_count(7, 'temp_coeffecient')  # ValueError: 7 is not a valid number of bands\n\n# after\nget_band_type_count(6, 'temp_coeffecient')  # 1","handlingStrategy":"validation","validationCode":"VALID_BAND_COUNTS = {3, 4, 5, 6}\nif not isinstance(total_number_of_bands, int) or total_number_of_bands not in VALID_BAND_COUNTS:\n    raise ValueError('band count must be one of 3, 4, 5, 6')","typeGuard":"def is_valid_band_count(n: object) -> bool:\n    return isinstance(n, int) and not isinstance(n, bool) and n in {3, 4, 5, 6}","tryCatchPattern":"try:\n    n = get_band_type_count(bands, band_type)\nexcept ValueError as exc:\n    if 'not a valid number of bands' in str(exc):\n        # recount bands / reject input\n        ...\n    elif 'not valid for a' in str(exc):\n        # band type unsupported at this count\n        ...\n    raise","preventionTips":["Coerce parsed band counts with int() before calling.","Only 3-6 band resistors are supported — validate first.","Distinguish the two ValueErrors this function can raise by message substring."],"tags":["electronics","resistor","color-code","validation","valueerror"],"backgroundTag":null,"analyzedSha":"f5988cc09713315817df6a7e327e258013a94440","analyzedAt":"2026-08-14T17:30:07.041Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}