Add duration property

captaintrain.py

@@ -106,7 +106,7 @@ class Trip:
         return "From %s at %s to %s at %s // duration: %s // price: %s %s // %s" % (
             self.departure_station.name, self.departure_date,
             self.arrival_station.name, self.arrival_date,
-            self.arrival_date - self.departure_date,
+            self.duration,
             self.price, self.currency,
             " + ".join([str(s) for s in self.segments])
             )
@@ -140,6 +140,10 @@ class Trip:
     def arrival_station(self):
         return self._arrival_station
 
+    @property
+    def duration(self):
+        return self._arrival_date - self._departure_date
+
     @property
     def segments(self):
         return self._segments