exercism/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 int(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 += exchange_rate * (spread / 100)
return (
get_number_of_bills(exchange_money(budget, exchange_rate), denomination)
* denomination
)