protein weight calculator

pWeights.py

#!/usr/bin/env python3
"""
Uses three sources of input and produces two forms of output regarding proteins and
their expected molecular weights for the purpose of mass spectrometry.
"""

import sys


try:
    with open(sys.argv[1], mode="w") as file:
        aminoMono = {}
        totalLength, totalWeight, length = 0, 0, 0
        with open("/srv/datasets/amino-monoisotopic-mass") as input_file:
            for line in input_file:
                line = line.split()
                aminoMono[line[0]] = float(line[1])

        for line in sys.stdin:
            line = line.strip()
            weight = 0
            for char in line:
                weight += aminoMono[char]

            totalLength += len(line)
            totalWeight += weight
            length += 1
            print(f"{line} {len(line)} {weight:.3f}", file=file)

        print(f"{length} {totalLength} {totalWeight:.3f}")
except IndexError:
    print("Why are you wasting electricity?")
    sys.exit(1)