final.py

#!/usr/bin/env python3

BOTTLES_PER_MONTH_PER_STUDENT = 156 / 12 # https://www.jerseyislandholidays.com/plastic-bottle-pollution-statistics
BOTTLE_PERCENT_PLASTIC = 0.291 # https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/plastics-material-specific-data
BOTTLE_PERCENT_RECYCLED = 0.09 # https://www.greenmatters.com/p/what-percent-recycling-actually-gets-recycled
AVERAGE_PLASTIC_GRAMS_PER_BOTTLE = 19 # https://www.wastecare.com/usefulinfo/PET-Plastic-Water-Soda-Bottles-Bale-Weights.htm
AVERAGE_PLASTIC_GRAMS_PER_ID = 5 # https://www.uscreditcardguide.com/the-most-heavy-credit-cards-list/


while True:
    try:
        num_students = int(input('Number of students at school: '))
        assert num_students > 0
        num_months = int(input('How often you want us to produce cards (in months): '))
        assert num_months > 0
    except (ValueError, AssertionError):
        print('Input must be an integer greater than 0')
        exit(1)
    except KeyboardInterrupt:
        print('Goodbye!')
        exit(0)

    total_bottles = BOTTLES_PER_MONTH_PER_STUDENT * num_students * num_months * BOTTLE_PERCENT_PLASTIC
    num_recycled_bottles = total_bottles * BOTTLE_PERCENT_RECYCLED
    amount_plastic_recycled = num_recycled_bottles * AVERAGE_PLASTIC_GRAMS_PER_BOTTLE

    print('------')
    print('Number of grams of recycleable waste plastic over %d months: %dkg' % (num_months, amount_plastic_recycled // 1000))

    num_ids = amount_plastic_recycled // AVERAGE_PLASTIC_GRAMS_PER_ID

    print('Number of ID cards we could produce: %d cards' % num_ids)
    print('Contact sales if your school would be interested in doing business with us!\n\n====================\n')