Calculating Protein Mass (ROSALIND PRTM)

Given: A protein string P of length at most 1000 aa.

Return: The total weight of P. Consult the monoisotopic mass table.

def mass_table():
    mt = {}
    mt['A'] = 71.03711 

    mt['C'] = 103.00919 

    mt['D'] = 115.02694

    mt['E'] = 129.04259

    mt['F'] = 147.06841 

    mt['G'] = 57.02146 

    mt['H'] = 137.05891 

    mt['I'] = 113.08406 

    mt['K'] = 128.09496 

    mt['L'] = 113.08406 

    mt['M'] = 131.04049

    mt['N'] = 114.04293 

    mt['P'] = 97.05276 

    mt['Q'] = 128.05858 

    mt['R'] = 156.10111 

    mt['S'] = 87.03203 

    mt['T'] = 101.04768 

    mt['V'] = 99.06841 

    mt['W'] = 186.07931

    mt['Y'] = 163.06333 

    return mt

protein = input()
mt = mass_table()
mass = 0 

for aa in protein:
    mass += mt[aa]
print(round(mass,3))