main.py

# element key : paired with atomic mass
periodicTable_atomic = {
    "H": 1.00797,
    "He": 4.00260,
    "Li": 6.941,
    "Be": 9.01218,
    "B": 10.81,
    "C": 12.011,
    "N": 14.0067,
    "O": 15.9994,
    "F": 18.998403,
    "Ne": 20.179,
    "Na": 22.98977,
    "Mg": 24.305,
    "Al": 26.98154,
    "Si": 28.0855,
    "P": 30.97376,
    "S": 32.06,
    "Cl": 35.453,
    "K": 39.0983,
    "Ar": 39.948,
    "Ca": 40.08,
    "Sc": 44.9559,
    "Ti": 47.90,
    "V": 50.9415,
    "Cr": 51.996,
    "Mn": 54.9380,
    "Fe": 55.847,
    "Ni": 58.70,
    "Co": 58.9332,
    "Cu": 63.546,
    "Zn": 65.38,
    "Ga": 69.72,
    "Ge": 72.59,
    "As": 74.9216,
    "Se": 78.96,
    "Br": 79.904,
    "Kr": 83.80,
    "Rb": 85.4678,
    "Sr": 87.62,
    "Y": 88.9059,
    "Zr": 91.22,
    "Nb": 92.9064,
    "Mo": 95.94,
    "Tc": 98,
    "Ru": 101.07,
    "Rh": 102.9055,
    "Pd": 106.4,
    "Ag": 107.868,
    "Cd": 112.41,
    "In": 114.82,
    "Sn": 118.69,
    "Sb": 121.75,
    "I": 126.9045,
    "Te": 127.60,
    "Xe": 131.30,
    "Cs": 132.9054,
    "Ba": 137.33,
    "La": 138.9055,
    "Ce": 140.12,
    "Pr": 140.9077,
    "Nd": 144.24,
    "Pm": 145,
    "Sm": 150.4,
    "Eu": 151.96,
    "Gd": 157.25,
    "Tb": 158.9254,
    "Dy": 162.50,
    "Ho": 164.9304,
    "Er": 167.26,
    "Tm": 168.9342,
    "Yb": 173.04,
    "Lu": 174.967,
    "Hf": 178.49,
    "Ta": 180.9479,
    "W": 183.85,
    "Re": 186.207,
    "Os": 190.2,
    "Ir": 192.22,
    "Pt": 195.09,
    "Au": 196.9665,
    "Hg": 200.59,
    "Tl": 204.37,
    "Pb": 207.2,
    "Bi": 208.9804,
    "Po": 209,
    "At": 210,
    "Rn": 222,
    "Fr": 223,
    "Ra": 226.0254,
    "Ac": 227.0278,
    "Th": 232.0381,
    "Pa": 231.0359,
    "U": 238.029,
    "Np": 237.0482,
    "Pu": 242,
    "Am": 243,
    "Cm": 247,
    "Bk": 247,
    "No": 250,
    "Cf": 251,
    "Es": 252,
    "Hs": 255,
    "Mt": 256,
    "Fm": 257,
    "Md": 258,
    "Lr": 260,
    "Rf": 261,
    "Bh": 262,
    "Db": 262,
    "Sg": 263,
    "Uun": 269,
    "Uuu": 272,
    "Uub": 277
}

alphabet_list = list('abcdefghijklmnopqrstuvwxyz'.upper())

def check_if_upper(letter):
    return letter in alphabet_list

def num_of_atoms(string):
    for i in range(len(string)):
        if string[i].isnumeric(): 
            return string.strip(string[i:]), int(string[i:])
    return string, 1
        
def compound_formula_parser(formula):
    formula_list = list(formula)
    elements_and_total_atoms = {}
    list_of_indexes = []
    for i in range(len(formula_list)):
        if check_if_upper(formula_list[i]):
            list_of_indexes.append(i)
    element_list = ["".join(formula_list[list_of_indexes[i]:list_of_indexes[i+1]]) if i != len(list_of_indexes)-1 
         else "".join(formula_list[list_of_indexes[i]:]) for i in range(len(list_of_indexes))]
    for i in element_list:
        symbol, num = num_of_atoms(i)
        elements_and_total_atoms[symbol] = num
    return elements_and_total_atoms

def calculate_percent_composition(elements_and_total_atoms):
    total_atomic_mass = 0
    percent_composition = {}
    for element, num_of_atoms in elements_and_total_atoms.items(): total_atomic_mass += periodicTable_atomic[element]*num_of_atoms
    for element, num_of_atoms in elements_and_total_atoms.items(): 
        percent_composition[element] = (periodicTable_atomic[element]*num_of_atoms/total_atomic_mass)*100
    return percent_composition

a = compound_formula_parser(input())
print(calculate_percent_composition(a))

# a = compound_formula_parser("Cu(OH)2")
# print(calculate_percent_composition(a))
# compound_formula_parser("Al(C2H3O2)3")  // Doesn't work with distribution