e018-prtm.py

#!/usr/bin/env python
# coding=utf-8

# Calculating Protein Mass
# ========================
# 
# In a weighted alphabet, every symbol is assigned a positive real number called
# a weight. A string formed from a weighted alphabet is called a weighted
# string, and its weight is equal to the sum of the weights of its symbols.
# 
# The standard weight assigned to each member of the 20-symbol amino acid
# alphabet is the monoisotopic mass of the corresponding amino acid.
# 
# Given: A protein string P of length at most 1000 aa.
# 
# Return: The weight of P to an accuracy of two decimal places. Consult the
# monoisotopic mass table.
# 
# Sample Dataset
# --------------
# SKADYEK
# 
# Sample Output
# -------------
# 821.39

MONOISOTOPIC_MASS_TABLE = {
    'A': 71.03711,
    'C': 103.00919,
    'D': 115.02694,
    'E': 129.04259,
    'F': 147.06841,
    'G': 57.02146,
    'H': 137.05891,
    'I': 113.08406,
    'K': 128.09496,
    'L': 113.08406,
    'M': 131.04049,
    'N': 114.04293,
    'P': 97.05276,
    'Q': 128.05858,
    'R': 156.10111,
    'S': 87.03203,
    'T': 101.04768,
    'V': 99.06841,
    'W': 186.07931,
    'Y': 163.06333,
}

def weight(weighted_string):
    n = 0
    for aa in weighted_string:
        n += MONOISOTOPIC_MASS_TABLE[aa]
    return n


if __name__ == "__main__":

    small_dataset = "SKADYEK"
    large_dataset = open('datasets/rosalind_prtm.txt').read().strip()

    print weight(large_dataset)