Title : Calculating the resistance of a n band resistor using the color codes Description : Resistors resist the flow of electrical current.Each one has a value that tells how strongly it resists current flow.This value's unit is the ohm, often noted with the Greek letter omega: . The colored bands on a resistor can tell you everything you need to know about its value and tolerance, as long as you understand how to read them. The order in which the colors are arranged is very important, and each value of resistor has its own unique combination. The color coding for resistors is an international standard that is defined in IEC 60062. The number of bands present in a resistor varies from three to six. These represent significant figures, multiplier, tolerance, reliability, and temperature coefficient Each color used for a type of band has a value assigned to it. It is read from left to right. All resistors will have significant figures and multiplier bands. In a three band resistor first two bands from the left represent significant figures and the third represents the multiplier band. Significant figures  The number of significant figures band in a resistor can vary from two to three. Colors and values associated with significant figure bands  Black  0, Brown  1, Red  2, Orange  3, Yellow  4, Green  5, Blue  6, Violet  7, Grey  8, White  9 Multiplier  There will be one multiplier band in a resistor. It is multiplied with the significant figures obtained from previous bands. Colors and values associated with multiplier band  Black  100, Brown  101, Red  102, Orange  103, Yellow  104, Green  105, Blue  106, Violet  107, Grey  108, White  109, Gold  101, Silver  102 Note that multiplier bands use Gold and Silver which are not used for significant figure bands. Tolerance  The tolerance band is not always present. It can be seen in four band resistors and above. This is a percentage by which the resistor value can vary. Colors and values associated with tolerance band  Brown  1, Red  2, Orange  0.05, Yellow  0.02, Green  0.5,Blue  0.25, Violet  0.1, Grey  0.01, Gold  5, Silver  10 If no color is mentioned then by default tolerance is 20 Note that tolerance band does not use Black and White colors. Temperature Coeffecient  Indicates the change in resistance of the component as a function of ambient temperature in terms of ppmK. It is present in six band resistors. Colors and values associated with Temperature coeffecient  Black  250 ppmK, Brown  100 ppmK, Red  50 ppmK, Orange  15 ppmK, Yellow  25 ppmK, Green  20 ppmK, Blue  10 ppmK, Violet  5 ppmK, Grey  1 ppmK Note that temperature coeffecient band does not use White, Gold, Silver colors. Sources : https:www.calculator.netresistorcalculator.html https:learn.parallax.comsupportreferenceresistorcolorcodes https:byjus.comphysicsresistorcolourcodes Function returns the digit associated with the color. Function takes a list containing colors as input and returns digits as string  getsignificantdigits'Black','Blue' '06'  getsignificantdigits'Aqua','Blue' Traceback most recent call last: ... ValueError: Aqua is not a valid color for significant figure bands Function returns the multiplier value associated with the color. Function takes color as input and returns multiplier value  getmultiplier'Gold' 0.1  getmultiplier'Ivory' Traceback most recent call last: ... ValueError: Ivory is not a valid color for multiplier band Function returns the tolerance value associated with the color. Function takes color as input and returns tolerance value.  gettolerance'Green' 0.5  gettolerance'Indigo' Traceback most recent call last: ... ValueError: Indigo is not a valid color for tolerance band Function returns the temperature coeffecient value associated with the color. Function takes color as input and returns temperature coeffecient value.  gettemperaturecoeffecient'Yellow' 25  gettemperaturecoeffecient'Cyan' Traceback most recent call last: ... ValueError: Cyan is not a valid color for temperature coeffecient band Function returns the number of bands of a given type in a resistor with n bands Function takes totalnumberofbands and typeofband as input and returns number of bands belonging to that type in the given resistor  getbandtypecount3,'significant' 2  getbandtypecount2,'significant' Traceback most recent call last: ... ValueError: 2 is not a valid number of bands  getbandtypecount3,'sign' Traceback most recent call last: ... ValueError: sign is not valid for a 3 band resistor  getbandtypecount3,'tolerance' Traceback most recent call last: ... ValueError: tolerance is not valid for a 3 band resistor  getbandtypecount5,'tempcoeffecient' Traceback most recent call last: ... ValueError: tempcoeffecient is not valid for a 5 band resistor Function checks if the input provided is valid or not. Function takes numberofbands and colors as input and returns True if it is valid  checkvalidity3, Black,Blue,Orange True  checkvalidity4, Black,Blue,Orange Traceback most recent call last: ... ValueError: Expecting 4 colors, provided 3 colors  checkvalidity3, Cyan,Red,Yellow Traceback most recent call last: ... ValueError: Cyan is not a valid color Function calculates the total resistance of the resistor using the color codes. Function takes numberofbands, colorcodelist as input and returns resistance  calculateresistance3, Black,Blue,Orange 'resistance': '6000 20 '  calculateresistance4, Orange,Green,Blue,Gold 'resistance': '35000000 5 '  calculateresistance5, Violet,Brown,Grey,Silver,Green 'resistance': '7.18 0.5 '  calculateresistance6, Red,Green,Blue,Yellow,Orange,Grey 'resistance': '2560000 0.05 1 ppmK'  calculateresistance0, Violet,Brown,Grey,Silver,Green Traceback most recent call last: ... ValueError: Invalid number of bands. Resistor bands must be 3 to 6  calculateresistance4, Violet,Brown,Grey,Silver,Green Traceback most recent call last: ... ValueError: Expecting 4 colors, provided 5 colors  calculateresistance4, Violet,Silver,Brown,Grey Traceback most recent call last: ... ValueError: Silver is not a valid color for significant figure bands  calculateresistance4, Violet,Blue,Lime,Grey Traceback most recent call last: ... ValueError: Lime is not a valid color
valid_colors: list = [
    "Black",
    "Brown",
    "Red",
    "Orange",
    "Yellow",
    "Green",
    "Blue",
    "Violet",
    "Grey",
    "White",
    "Gold",
    "Silver",
]

significant_figures_color_values: dict[str, int] = {
    "Black": 0,
    "Brown": 1,
    "Red": 2,
    "Orange": 3,
    "Yellow": 4,
    "Green": 5,
    "Blue": 6,
    "Violet": 7,
    "Grey": 8,
    "White": 9,
}

multiplier_color_values: dict[str, float] = {
    "Black": 10**0,
    "Brown": 10**1,
    "Red": 10**2,
    "Orange": 10**3,
    "Yellow": 10**4,
    "Green": 10**5,
    "Blue": 10**6,
    "Violet": 10**7,
    "Grey": 10**8,
    "White": 10**9,
    "Gold": 10**-1,
    "Silver": 10**-2,
}

tolerance_color_values: dict[str, float] = {
    "Brown": 1,
    "Red": 2,
    "Orange": 0.05,
    "Yellow": 0.02,
    "Green": 0.5,
    "Blue": 0.25,
    "Violet": 0.1,
    "Grey": 0.01,
    "Gold": 5,
    "Silver": 10,
}

temperature_coeffecient_color_values: dict[str, int] = {
    "Black": 250,
    "Brown": 100,
    "Red": 50,
    "Orange": 15,
    "Yellow": 25,
    "Green": 20,
    "Blue": 10,
    "Violet": 5,
    "Grey": 1,
}

band_types: dict[int, dict[str, int]] = {
    3: {"significant": 2, "multiplier": 1},
    4: {"significant": 2, "multiplier": 1, "tolerance": 1},
    5: {"significant": 3, "multiplier": 1, "tolerance": 1},
    6: {"significant": 3, "multiplier": 1, "tolerance": 1, "temp_coeffecient": 1},
}


def get_significant_digits(colors: list) -> str:
    """
    Function returns the digit associated with the color. Function takes a
    list containing colors as input and returns digits as string

    >>> get_significant_digits(['Black','Blue'])
    '06'

    >>> get_significant_digits(['Aqua','Blue'])
    Traceback (most recent call last):
      ...
    ValueError: Aqua is not a valid color for significant figure bands

    """
    digit = ""
    for color in colors:
        if color not in significant_figures_color_values:
            msg = f"{color} is not a valid color for significant figure bands"
            raise ValueError(msg)
        digit = digit + str(significant_figures_color_values[color])
    return str(digit)


def get_multiplier(color: str) -> float:
    """
    Function returns the multiplier value associated with the color.
    Function takes color as input and returns multiplier value

    >>> get_multiplier('Gold')
    0.1

    >>> get_multiplier('Ivory')
    Traceback (most recent call last):
      ...
    ValueError: Ivory is not a valid color for multiplier band

    """
    if color not in multiplier_color_values:
        msg = f"{color} is not a valid color for multiplier band"
        raise ValueError(msg)
    return multiplier_color_values[color]


def get_tolerance(color: str) -> float:
    """
    Function returns the tolerance value associated with the color.
    Function takes color as input and returns tolerance value.

    >>> get_tolerance('Green')
    0.5

    >>> get_tolerance('Indigo')
    Traceback (most recent call last):
      ...
    ValueError: Indigo is not a valid color for tolerance band

    """
    if color not in tolerance_color_values:
        msg = f"{color} is not a valid color for tolerance band"
        raise ValueError(msg)
    return tolerance_color_values[color]


def get_temperature_coeffecient(color: str) -> int:
    """
    Function returns the temperature coeffecient value associated with the color.
    Function takes color as input and returns temperature coeffecient value.

    >>> get_temperature_coeffecient('Yellow')
    25

    >>> get_temperature_coeffecient('Cyan')
    Traceback (most recent call last):
      ...
    ValueError: Cyan is not a valid color for temperature coeffecient band

    """
    if color not in temperature_coeffecient_color_values:
        msg = f"{color} is not a valid color for temperature coeffecient band"
        raise ValueError(msg)
    return temperature_coeffecient_color_values[color]


def get_band_type_count(total_number_of_bands: int, type_of_band: str) -> int:
    """
    Function returns the number of bands of a given type in a resistor with n bands
    Function takes total_number_of_bands and type_of_band as input and returns
    number of bands belonging to that type in the given resistor

    >>> get_band_type_count(3,'significant')
    2

    >>> get_band_type_count(2,'significant')
    Traceback (most recent call last):
      ...
    ValueError: 2 is not a valid number of bands

    >>> get_band_type_count(3,'sign')
    Traceback (most recent call last):
      ...
    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"])
    Traceback (most recent call last):
      ...
    ValueError: Cyan is not a valid color

    """
    if number_of_bands >= 3 and number_of_bands <= 6:
        if number_of_bands == len(colors):
            for color in colors:
                if color not in valid_colors:
                    msg = f"{color} is not a valid color"
                    raise ValueError(msg)
            return True
        else:
            msg = f"Expecting {number_of_bands} colors, provided {len(colors)} colors"
            raise ValueError(msg)
    else:
        msg = "Invalid number of bands. Resistor bands must be 3 to 6"
        raise ValueError(msg)


def calculate_resistance(number_of_bands: int, color_code_list: list) -> dict:
    """
    Function calculates the total resistance of the resistor using the color codes.
    Function takes number_of_bands, color_code_list as input and returns
    resistance

    >>> calculate_resistance(3, ["Black","Blue","Orange"])
    {'resistance': '6000Ω ±20% '}

    >>> calculate_resistance(4, ["Orange","Green","Blue","Gold"])
    {'resistance': '35000000Ω ±5% '}

    >>> calculate_resistance(5, ["Violet","Brown","Grey","Silver","Green"])
    {'resistance': '7.18Ω ±0.5% '}

    >>> calculate_resistance(6, ["Red","Green","Blue","Yellow","Orange","Grey"])
    {'resistance': '2560000Ω ±0.05% 1 ppm/K'}

    >>> calculate_resistance(0, ["Violet","Brown","Grey","Silver","Green"])
    Traceback (most recent call last):
      ...
    ValueError: Invalid number of bands. Resistor bands must be 3 to 6

    >>> calculate_resistance(4, ["Violet","Brown","Grey","Silver","Green"])
    Traceback (most recent call last):
      ...
    ValueError: Expecting 4 colors, provided 5 colors

    >>> calculate_resistance(4, ["Violet","Silver","Brown","Grey"])
    Traceback (most recent call last):
      ...
    ValueError: Silver is not a valid color for significant figure bands

    >>> calculate_resistance(4, ["Violet","Blue","Lime","Grey"])
    Traceback (most recent call last):
      ...
    ValueError: Lime is not a valid color

    """
    is_valid = check_validity(number_of_bands, color_code_list)
    if is_valid:
        number_of_significant_bands = get_band_type_count(
            number_of_bands, "significant"
        )
        significant_colors = color_code_list[:number_of_significant_bands]
        significant_digits = int(get_significant_digits(significant_colors))
        multiplier_color = color_code_list[number_of_significant_bands]
        multiplier = get_multiplier(multiplier_color)
        if number_of_bands == 3:
            tolerance_color = None
        else:
            tolerance_color = color_code_list[number_of_significant_bands + 1]
        tolerance = (
            20 if tolerance_color is None else get_tolerance(str(tolerance_color))
        )
        if number_of_bands != 6:
            temperature_coeffecient_color = None
        else:
            temperature_coeffecient_color = color_code_list[
                number_of_significant_bands + 2
            ]
        temperature_coeffecient = (
            0
            if temperature_coeffecient_color is None
            else get_temperature_coeffecient(str(temperature_coeffecient_color))
        )
        resisitance = significant_digits * multiplier
        if temperature_coeffecient == 0:
            answer = f"{resisitance}Ω ±{tolerance}% "
        else:
            answer = f"{resisitance}Ω ±{tolerance}% {temperature_coeffecient} ppm/K"
        return {"resistance": answer}
    else:
        raise ValueError("Input is invalid")


if __name__ == "__main__":
    import doctest

    doctest.testmod()
