generate Event.args_map on request and cache instead of instaniating …

…object

boa/vyper/contract.py

@@ -627,8 +627,7 @@ def decode_log(self, e):
                 a_i += 1
 
         event_name = ", ".join(f"{k}={v}" for k, v in decoded_values)
-        args_map = dict([(k,v) for k, v in decoded_values])
-        return Event(log_id, self.address, event_t, event_name, decoded_topics, args, args_map)
+        return Event(log_id, self.address, event_t, event_name, decoded_topics, args)
 
     def marshal_to_python(self, computation, vyper_typ):
         self._computation = computation  # for further inspection

boa/vyper/event.py

@@ -1,3 +1,4 @@
+import functools
 from dataclasses import dataclass
 from typing import Any, List, Dict
 
@@ -11,11 +12,14 @@ class Event:
     event_name: str # human readable output
     topics: List[Any]  # list of decoded topics
     args: List[Any]  # list of decoded args
-    args_map: Dict[str, Any]  # Mapping of decoded args
 
     def __repr__(self):
         return self.event_name
-
+
+    @functools.cached_property
+    def args_map(self):
+        event_values = self.event_name.split(', ')
+        return dict([(topic.split('=')) for topic in event_values])
 
 class RawEvent:
-    event_data: Any
+    event_data: Any