credit_calculator.py

from collections import namedtuple


CreditCondition = namedtuple(
    'CreditCondition',
    ['property_value',
     'initial_payment',
     'loan_months',
     'interest_rate'])


class CreditCalculator:
    def __init__(self,
                 property_value,
                 initial_payment,
                 loan_months,
                 interest_rate):
        self.property_value = property_value
        self.initial_payment = initial_payment
        self.loan_months = loan_months
        self.interest_rate = interest_rate

    @property
    def loan_amount(self):
        return self.property_value - self.initial_payment

    @property
    def monthly_payment(self):
        coef_months = (1 + self.interest_rate / 12) ** self.loan_months
        return self.loan_amount * self.interest_rate / 12 * coef_months / (coef_months - 1)

    @property
    def overpayment(self):
        return self.monthly_payment * self.loan_months - self.loan_amount


def main():
    while True:
        print('Введите данные для расчёта кредита')

        fields = dict(
            property_value=dict(text='Стоимость недвижимости', value=0),
            initial_payment=dict(text='Первоначальный взнос', value=0),
            loan_months=dict(text='Период кредита в месяцах', value=0),
            interest_rate=dict(text='Процентная ставка (%)', value=0),
        )

        for code, field in fields.items():
            value = input(f"{field['text']}: ")
            try:
                value = float(value)
                if value > 0:
                    fields[code]['value'] = value
            except Exception as ex:
                print(f'Введено некорректное значение: {value}')
                print(ex)
                break
        data = CreditCondition(*[field['value']
                                 for field in fields.values()])
        credit = CreditCalculator(
            property_value=data.property_value,
            initial_payment=data.initial_payment,
            loan_months=data.loan_months,
            interest_rate=data.interest_rate / 100)

        print('Стоимость недвижимости:', credit.property_value)
        print('Первоначальный взнос:', credit.initial_payment)
        print('Процентная ставка (%)', credit.interest_rate * 100)
        print('Период кредита в месяцах:', credit.loan_months)
        print('Размер кредита:', credit.loan_amount)
        print('Ежемесячный платёж:', credit.monthly_payment)
        print('Переплата:', credit.overpayment)

        if input('Для выхода введите exit: ').lower() == 'exit':
            break
        print('\n')


if __name__ == '__main__':
    main()