IfcOpenShell/src/ifcopenshell-python/ifcopenshell/util/unit.py

from math import pi

prefixes = {'EXA': 1e18, 'PETA': 1e15, 'TERA': 1e12, 'GIGA': 1e9, 'MEGA':
    1e6, 'KILO': 1e3, 'HECTO': 1e2, 'DECA': 1e1, 'DECI': 1e-1, 'CENTI':
    1e-2, 'MILLI': 1e-3, 'MICRO': 1e-6, 'NANO': 1e-9, 'PICO': 1e-12,
    'FEMTO': 1e-15, 'ATTO': 1e-18}

unit_names = ['AMPERE', 'BECQUEREL', 'CANDELA', 'COULOMB',
    'CUBIC_METRE', 'DEGREE CELSIUS', 'FARAD', 'GRAM', 'GRAY', 'HENRY',
    'HERTZ', 'JOULE', 'KELVIN', 'LUMEN', 'LUX', 'MOLE', 'NEWTON', 'OHM',
    'PASCAL', 'RADIAN', 'SECOND', 'SIEMENS', 'SIEVERT', 'SQUARE METRE',
    'METRE', 'STERADIAN', 'TESLA', 'VOLT', 'WATT', 'WEBER']

si_conversions = {
    'inch': 0.0254,
    'foot': 0.3048,
    'yard': 0.914,
    'mile': 1609,
    'square inch': 0.0006452,
    'square foot': 0.09290304,
    'square yard': 0.83612736,
    'acre': 4046.86,
    'square mile': 2588881,
    'cubic inch': 0.00001639,
    'cubic foot': 0.02831684671168849,
    'cubic yard': 0.7636,
    'litre': 0.001,
    'fluid ounce UK': 0.0000284130625,
    'fluid ounce US': 0.00002957353,
    'pint UK': 0.000568,
    'pint US': 0.000473,
    'gallon UK': 0.004546,
    'gallon US': 0.003785,
    'degree': pi/180,
    'ounce': 0.02835,
    'pound': 0.454,
    'ton UK': 1016.0469088,
    'ton US': 907.18474,
    'lbf': 4.4482216153,
    'kip': 4448.2216153,
    'psi': 6894.7572932,
    'ksi': 6894757.2932,
    'minute': 60,
    'hour': 3600,
    'day': 86400,
    'btu': 1055.056}

def get_prefix(text):
    for prefix in prefixes.keys():
        if prefix in text.upper():
            return prefix

def get_prefix_multiplier(text):
    if not text:
        return 1
    prefix = get_prefix(text)
    if prefix:
        return prefixes[prefix]
    return 1

def get_unit_name(text):
    for name in unit_names:
        if name in text.upper().replace('METER', 'METRE'):
            return name

def convert(value, from_prefix, from_unit, to_prefix, to_unit):
    """Converts between length, area, and volume units

    :param value: The numeric value you want to convert
    :type value: float
    :param from_prefix: A prefix from IfcSIPrefix. Can be None.
    :type from_prefix: string
    :param from_unit: IfcSIUnitName or IfcConversionBasedUnit.Name
    :type from_unit: string
    :param to_prefix: A prefix from IfcSIPrefix. Can be None.
    :type to_prefix: string
    :param to_unit: IfcSIUnitName or IfcConversionBasedUnit.Name
    :type to_unit: string
    """
    if from_unit in si_conversions:
        value *= si_conversions[from_unit]
    elif from_prefix:
        value *= get_prefix_multiplier(from_prefix)
        if 'SQUARE' in from_unit:
            value *= get_prefix_multiplier(from_prefix)
        elif 'CUBIC' in from_unit:
            value *= get_prefix_multiplier(from_prefix)
            value *= get_prefix_multiplier(from_prefix)
    if to_unit in si_conversions:
        return value * (1 / si_conversions[to_unit])
    elif to_prefix:
        value *= (1 / get_prefix_multiplier(to_prefix))
        if 'SQUARE' in from_unit:
            value *= (1 / get_prefix_multiplier(to_prefix))
        elif 'CUBIC' in from_unit:
            value *= (1 / get_prefix_multiplier(to_prefix))
            value *= (1 / get_prefix_multiplier(to_prefix))
    return value