feat(event-sources): cache parsed json in data class

A micro optimization to cache the parsed json within the event source data class

Author: Michael Brewer

aws_lambda_powertools/utilities/data_classes/common.py

@@ -45,6 +45,10 @@ def get_header_value(
 
 
 class BaseProxyEvent(DictWrapper):
+ def __init__(self, data: Dict[str, Any]):
+ super().__init__(data)
+ self._parsed_json_body: Optional[Any] = None
+
  @property
  def headers(self) -> Dict[str, str]:
  return self["headers"]
@@ -65,7 +69,11 @@ def body(self) -> Optional[str]:
  @property
  def json_body(self) -> Any:
  """Parses the submitted body as json"""
- return json.loads(self.decoded_body)
+ if self._parsed_json_body:
+ return self._parsed_json_body
+
+ self._parsed_json_body = json.loads(self.decoded_body)
+ return self._parsed_json_body
 
  @property
  def decoded_body(self) -> str:

tests/functional/test_data_classes.py

@@ -1053,7 +1053,9 @@ def test_base_proxy_event_json_body_key_error():
 def test_base_proxy_event_json_body():
  data = {"message": "Foo"}
  event = BaseProxyEvent({"body": json.dumps(data)})
+ assert event._parsed_json_body is None
  assert event.json_body == data
+ assert event.json_body == event._parsed_json_body == data
 
 
 def test_base_proxy_event_decode_body_key_error():
@@ -1084,7 +1086,7 @@ def test_base_proxy_event_json_body_with_base64_encoded_data():
  event = BaseProxyEvent({"body": encoded_data, "isBase64Encoded": True})
 
  # WHEN calling json_body
- # THEN then base64 decode and json load
+ # THEN base64 decode and json load
  assert event.json_body == data