tip-calculator.py

#!/usr/bin/env python3

import math
from prettytable import PrettyTable


def main():
    params = {
        'amount': 12.34,
        'split': 1
    }
    render_table(**params)


class TipTable(PrettyTable):
    def __init__(self, field_names=None, **kwargs):
        filtered = TipTable.filter_list(field_names)
        super().__init__(filtered, **kwargs)
        self.float_format = '0.2'
        self.align = 'r'

    def add_row(self, row):
        filtered = TipTable.filter_list(row)
        return super().add_row(filtered)

    @staticmethod
    def filter_list(array):
        if not array:
            return []
        return list(filter(lambda x: x is not None, array))


def render_table(amount, split=1):
    tip_amounts = [0.15, 0.18, 0.20, 0.25, 0.30]
    split = max(split, 1)
    amount = abs(amount)

    def show_value(value):
        return value if split > 1 else None

    headers = [
        '%',
        'Tip',
        show_value('Each (%s)' % split),
        show_value('Split'),
        'Total'
    ]
    table = TipTable(headers)
    table_rounded = TipTable(headers)

    for percentage in tip_amounts:
        tip = (amount * (1 + percentage)) - amount
        total = amount + tip

        row = [
            percentage,
            tip,
            show_value(tip / split),
            show_value((total / split)),
            total
        ]
        table.add_row(row)

        # create rounded tips table
        total_rounded = float(math.ceil(total))
        tip_rounded = total_rounded - total + tip

        row_rounded = [
            percentage,
            tip_rounded,
            show_value(tip_rounded / split),
            show_value(total_rounded / split),
            total_rounded
        ]
        table_rounded.add_row(row_rounded)
    print('Amount: %s' % amount)
    print('Exact:')
    print(table)
    print('')
    print('Rounded:')
    print(table_rounded)


if __name__ == '__main__':
    main()