fetching and writing rates

xexe/exchange_rates.py

@@ -0,0 +1,47 @@
+import datetime
+from typing import Iterable, Union
+
+from money.currency import Currency
+from money.money import Money
+
+
+class ExchangeRate:
+
+    def __init__(
+        self,
+        from_currency: Currency,
+        to_currency: Currency,
+        rate: Money,
+        rate_date: datetime.date,
+    ) -> None:
+        self.from_currency = from_currency
+        self.to_currency = to_currency
+        self.rate = rate
+        self.rate_date = rate_date
+
+    @property
+    def descriptor(self) -> str:
+        return (
+            str(self.from_currency.value)
+            + str(self.to_currency.value)
+            + str(self.rate_date.strformat("%Y-%m-%d"))
+        )
+
+
+class ExchangeRates:
+
+    def __init__(self, rates: Union[Iterable[ExchangeRate], None] = None):
+
+        self._rate_index = {}
+
+        if rates is not None:
+            for rate in rates:
+                if not isinstance(rate, ExchangeRate):
+                    raise TypeError("ExchangeRates can only hold Rates.")
+                self._rate_index[rate.descriptor] = rate
+
+    def add_rate(self, new_rate: ExchangeRate) -> None:
+        self._rate_index[new_rate.descriptor] = new_rate
+
+    def __iter__(self):
+        return iter(self._rate_index.values())