expenser.py

from decimal import Decimal
import sys

if len(sys.argv) != 2:
    print('Usage: expenser.py <filename>')
    sys.exit()

exp = open(sys.argv[1], 'r')
amounts = []
count = 0

for line in exp:
    line = line.strip()
    
    if line:
        try:
            amounts.append(Decimal(line))
            count += 1
        except:
            print("Couldn't parse '%s'. Moving on..." % line)

total = sum(amounts)
print("Total: $%s" % total)
print("Mean: $%.02f" % (total / count))