Lazy load currency data from json file

Removing duplicate code, and preventing redundant disk reads

Author: Robbie-Palmer

forex_python/converter.py

@@ -118,20 +118,22 @@ def convert(self, base_cur, dest_cur, amount, date_obj=None):
 class CurrencyCodes:
 
     def __init__(self):
-        pass
+        self.__currency_data = None
+
+    @property
+    def _currency_data(self):
+        if self.__currency_data is None:
+            file_path = os.path.dirname(os.path.abspath(__file__))
+            with open(file_path + '/raw_data/currencies.json') as f:
+                self.__currency_data = json.loads(f.read())
+        return self.__currency_data
 
     def _get_data(self, currency_code):
-        file_path = os.path.dirname(os.path.abspath(__file__))
-        with open(file_path + '/raw_data/currencies.json') as f:
-            currency_data = json.loads(f.read())
-        currency_dict = next((item for item in currency_data if item["cc"] == currency_code), None)
+        currency_dict = next((item for item in self._currency_data if item["cc"] == currency_code), None)
         return currency_dict
 
     def _get_data_from_symbol(self, symbol):
-        file_path = os.path.dirname(os.path.abspath(__file__))
-        with open(file_path + '/raw_data/currencies.json') as f:
-            currency_data = json.loads(f.read())
-        currency_dict = next((item for item in currency_data if item["symbol"] == symbol), None)
+        currency_dict = next((item for item in self._currency_data if item["symbol"] == symbol), None)
         return currency_dict
 
     def get_symbol(self, currency_code):