primeiro commit com exercicios de Exercism realizados até esta data

python/currency-exchange/exchange.py

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+"""Functions for calculating steps in exchanging currency.
+
+Python numbers documentation: https://docs.python.org/3/library/stdtypes.html#numeric-types-int-float-complex
+
+Overview of exchanging currency when travelling: https://www.compareremit.com/money-transfer-tips/guide-to-exchanging-currency-for-overseas-travel/
+"""
+
+
+def exchange_money(budget, exchange_rate):
+    """
+
+    :param budget: float - amount of money you are planning to exchange.
+    :param exchange_rate: float - unit value of the foreign currency.
+    :return: float - exchanged value of the foreign currency you can receive.
+    """
+    return budget / exchange_rate
+
+
+def get_change(budget, exchanging_value):
+    """
+
+    :param budget: float - amount of money you own.
+    :param exchanging_value: float - amount of your money you want to exchange now.
+    :return: float - amount left of your starting currency after exchanging.
+    """
+    return budget - exchanging_value
+
+
+def get_value_of_bills(denomination, number_of_bills):
+    """
+
+    :param denomination: int - the value of a bill.
+    :param number_of_bills: int - total number of bills.
+    :return: int - calculated value of the bills.
+    """
+    return denomination * number_of_bills
+
+
+def get_number_of_bills(amount, denomination):
+    """
+
+    :param amount: float - the total starting value.
+    :param denomination: int - the value of a single bill.
+    :return: int - number of bills that can be obtained from the amount.
+    """
+    return amount // denomination
+
+
+def get_leftover_of_bills(amount, denomination):
+    """
+
+    :param amount: float - the total starting value.
+    :param denomination: int - the value of a single bill.
+    :return: float - the amount that is "leftover", given the current denomination.
+    """
+    return amount % denomination
+
+
+def exchangeable_value(budget, exchange_rate, spread, denomination):
+    """
+
+    :param budget: float - the amount of your money you are planning to exchange.
+    :param exchange_rate: float - the unit value of the foreign currency.
+    :param spread: int - percentage that is taken as an exchange fee.
+    :param denomination: int - the value of a single bill.
+    :return: int - maximum value you can get.
+    """
+    exchange_rate_with_spread = exchange_rate * (1 + (spread / 100))
+    max_amount_to_exhange = exchange_money(budget, exchange_rate_with_spread)
+    return denomination * get_number_of_bills(max_amount_to_exhange, denomination)