Alcohol by volume (ABV) calculator based on original and final beer gravity readings.

abv-calculator.py

#!/usr/bin/python
import sys

# Get the original and final gravity from the commandline args
try:
    og = float(sys.argv[1])
    fg = float(sys.argv[2])
except IndexError:
    print 'Usage %s <original gravity> <final gravity>' % sys.argv[0]
    sys.exit(1)

# Calculate and print the ABV
abv = ((((1.05) * (og - fg)) / fg) / 0.79) * 100
print '%.1f%%' % abv