Calculates Molar Mass of Elements

molar_mass.py

"""
=================================
Molar Mass Calculator
Author: Elijah Lopez
Version: 1.2.1
Last Updated: April 4th 2020
Created: July 8th 2017
Python Version: 3.6+
=================================
"""
MM_of_Elements = {'H': 1.00794, 'He': 4.002602, 'Li': 6.941, 'Be': 9.012182, 'B': 10.811, 'C': 12.0107, 'N': 14.0067,
                  'O': 15.9994, 'F': 18.9984032, 'Ne': 20.1797, 'Na': 22.98976928, 'Mg': 24.305, 'Al': 26.9815386,
                  'Si': 28.0855, 'P': 30.973762, 'S': 32.065, 'Cl': 35.453, 'Ar': 39.948, 'K': 39.0983, 'Ca': 40.078,
                  'Sc': 44.955912, 'Ti': 47.867, 'V': 50.9415, 'Cr': 51.9961, 'Mn': 54.938045,
                  'Fe': 55.845, 'Co': 58.933195, 'Ni': 58.6934, 'Cu': 63.546, 'Zn': 65.409, 'Ga': 69.723, 'Ge': 72.64,
                  'As': 74.9216, 'Se': 78.96, 'Br': 79.904, 'Kr': 83.798, 'Rb': 85.4678, 'Sr': 87.62, 'Y': 88.90585,
                  'Zr': 91.224, 'Nb': 92.90638, 'Mo': 95.94, 'Tc': 98.9063, 'Ru': 101.07, 'Rh': 102.9055, 'Pd': 106.42,
                  'Ag': 107.8682, 'Cd': 112.411, 'In': 114.818, 'Sn': 118.71, 'Sb': 121.760, 'Te': 127.6,
                  'I': 126.90447, 'Xe': 131.293, 'Cs': 132.9054519, 'Ba': 137.327, 'La': 138.90547, 'Ce': 140.116,
                  'Pr': 140.90465, 'Nd': 144.242, 'Pm': 146.9151, 'Sm': 150.36, 'Eu': 151.964, 'Gd': 157.25,
                  'Tb': 158.92535, 'Dy': 162.5, 'Ho': 164.93032, 'Er': 167.259, 'Tm': 168.93421, 'Yb': 173.04,
                  'Lu': 174.967, 'Hf': 178.49, 'Ta': 180.9479, 'W': 183.84, 'Re': 186.207, 'Os': 190.23, 'Ir': 192.217,
                  'Pt': 195.084, 'Au': 196.966569, 'Hg': 200.59, 'Tl': 204.3833, 'Pb': 207.2, 'Bi': 208.9804,
                  'Po': 208.9824, 'At': 209.9871, 'Rn': 222.0176, 'Fr': 223.0197, 'Ra': 226.0254, 'Ac': 227.0278,
                  'Th': 232.03806, 'Pa': 231.03588, 'U': 238.02891, 'Np': 237.0482, 'Pu': 244.0642, 'Am': 243.0614,
                  'Cm': 247.0703, 'Bk': 247.0703, 'Cf': 251.0796, 'Es': 252.0829, 'Fm': 257.0951, 'Md': 258.0951,
                  'No': 259.1009, 'Lr': 262, 'Rf': 267, 'Db': 268, 'Sg': 271, 'Bh': 270, 'Hs': 269, 'Mt': 278,
                  'Ds': 281, 'Rg': 281, 'Cn': 285, 'Nh': 284, 'Fl': 289, 'Mc': 289, 'Lv': 292, 'Ts': 294, 'Og': 294,
                  '': 0}


def molar_mass(compound: str, decimal_places=None) -> float:
    is_polyatomic = end = multiply = False
    polyatomic_mass, m_m, multiplier = 0, 0, 1
    element = ''

    for e in compound:
        if is_polyatomic:
            if end:
                is_polyatomic = False
                m_m += int(e) * polyatomic_mass if e.isdigit() else polyatomic_mass + MM_of_Elements[e]
            elif e.isdigit():
                multiplier = int(str(multiplier) + e) if multiply else int(e)
                multiply = True
            elif e.islower():
                element += e
            elif e.isupper():
                polyatomic_mass += multiplier * MM_of_Elements[element]
                element, multiplier, multiply = e, 1, False
            elif e == ')':
                polyatomic_mass += multiplier * MM_of_Elements[element]
                element, multiplier = '', 1
                end, multiply = True, False
        elif e == '(':
            m_m += multiplier * MM_of_Elements[element]
            element, multiplier = '', 1
            is_polyatomic, multiply = True, False
        elif e.isdigit():
            multiplier = int(str(multiplier) + e) if multiply else int(e)
            multiply = True
        elif e.islower():
            element += e
        elif e.isupper():
            m_m += multiplier * MM_of_Elements[element]
            element, multiplier, multiply = e, 1, False
    m_m += multiplier * MM_of_Elements[element]
    if decimal_places is not None:
        return round(m_m, decimal_places)
    return m_m


if __name__ == '__main__':
    # TESTS
    assert molar_mass('H') == 1.00794
    assert 18.015 < molar_mass('H2O') < 18.016
    assert 98.07 < molar_mass('H2SO4') < 98.08
    assert 386 < molar_mass('CF3OCF(CF3)CF2OCF2OCF3') < 386.1
    assert 159.6 < molar_mass('Fe2O3') < 159.7
    # OPTIONS
    DECIMAL_PLACES = 2

    user_input = input('\nEnter Compound Formula: ')
    print(f'The Molar mass of {user_input} is {molar_mass(user_input, DECIMAL_PLACES)} g/mol')

Can I propose a change? I have used this code to calculate some molar masses. But they had the following format which led to an error.
CF3OCF(CF3)CF2OCF2OCF3
The string after the parenthesis leads to an error as the code attempts to int(e) which is in this case 'C'
One solution would be to add:

if end:
    is_polyatomic = False
    if e.isdigit:
        m_m += int(e) * polyatomic_mass
    else:
        m_m += polyatomic_mass

Thank you for making this.

Thanks for the feedback, my program works for that now. I'm going to edit it again just to make it more Pythonic.

Just somethings to note as your patch was incorrect.

You can use three "`" to syntax highlight your code.
it's isidigit() not .isdigit