exchange rate discovery object.

lib/exchange_rate.py

@@ -0,0 +1,14 @@
+class Exchanger:
+
+    def __init__(self, quote_currencies):
+        self.quote_currencies = quote_currencies
+
+    def exchange(self, btc_amount, quote_currency):
+        assert quote_currency in self.quote_currencies
+
+        return btc_amount * 6
+
+if __name__ == "__main__":
+    exch = Exchanger(("EUR", "USD", "GBP"))
+    print exch.exchange(1, "EUR")
+