Switch to use_datetime

Author: huonw

aws_lambda_powertools/logging/formatter.py

@@ -62,7 +62,7 @@ def __init__(
         json_deserializer: Optional[Callable[[Union[Dict, str, bool, int, float]], str]] = None,
         json_default: Optional[Callable[[Any], Any]] = None,
         datefmt: Optional[str] = None,
-        datetime_fmt: Optional[str] = None,
+        use_datetime: bool = False,
         log_record_order: Optional[List[str]] = None,
         utc: bool = False,
         **kwargs,
@@ -88,13 +88,12 @@ def __init__(
             Only used when no custom JSON encoder is set
 
         datefmt : str, optional
-            String directives (strftime) to format log timestamp using `time`. Only one of `datefmt`
-            and `datetime_fmt` should be specified.
+            String directives (strftime) to format log timestamp.
 
-            See https://docs.python.org/3/library/time.html#time.strftime
-        datetime_fmt : str, optional
-            String directives (strftime) to format log timestamp using `datetime`. Only one of
-            `datefmt` and `datetime_fmt` should be specified.
+            See https://docs.python.org/3/library/time.html#time.strftime or
+        use_datetime: str, optional
+            Interpret `datefmt` as a format string for `datetime.datetime.strftime`, rather than
+            `time.strftime`.
 
             See https://docs.python.org/3/library/datetime.html#strftime-strptime-behavior . This
             also supports a custom %F directive for milliseconds.
@@ -110,10 +109,8 @@ def __init__(
         self.json_default = json_default or str
         self.json_serializer = json_serializer or partial(json.dumps, default=self.json_default, separators=(",", ":"))
 
-        if datefmt and datetime_fmt:
-            raise ValueError(f"at most one of datefmt {datefmt!r} and datetime_fmt {datetime_fmt!r} can be specified")
         self.datefmt = datefmt
-        self.datetime_fmt = datetime_fmt
+        self.use_datetime = use_datetime
 
         self.utc = utc
         self.log_record_order = log_record_order or ["level", "location", "message", "timestamp"]
@@ -145,25 +142,28 @@ def format(self, record: logging.LogRecord) -> str:  # noqa: A003
     def formatTime(self, record: logging.LogRecord, datefmt: Optional[str] = None) -> str:
         record_ts = self.converter(record.created)  # type: ignore
 
+        if datefmt is None:
+            datefmt = self.datefmt
+
         # NOTE: Python `time.strftime` doesn't provide msec directives
         # so we create a custom one (%F) and replace logging record ts
         # Reason 2 is that std logging doesn't support msec after TZ
         msecs = "%03d" % record.msecs
 
-        if datefmt or self.datefmt:
-            return time.strftime(datefmt or self.datefmt, record_ts)
-
-        elif self.datetime_fmt:
+        if self.use_datetime:
             timestamp = record.created + record.msecs / 1000
 
             dt = datetime.fromtimestamp(timestamp, tz=timezone.utc)
             if not self.utc:
                 # convert back to local time
                 dt = dt.astimezone()
 
-            custom_fmt = self.datetime_fmt.replace(self.custom_ms_time_directive, msecs)
+            custom_fmt = (datefmt or self.default_time_format).replace(self.custom_ms_time_directive, msecs)
             return dt.strftime(custom_fmt)
 
+        elif datefmt:
+            return time.strftime(datefmt, record_ts)
+
         custom_fmt = self.default_time_format.replace(self.custom_ms_time_directive, msecs)
         return time.strftime(custom_fmt, record_ts)
 

aws_lambda_powertools/logging/logger.py

@@ -81,10 +81,13 @@ class Logger(logging.Logger):  # lgtm [py/missing-call-to-init]
     ---------------------------------------------
     datefmt: str, optional
         String directives (strftime) to format log timestamp using `time`, by default it uses RFC
-        3339. Only one of `datefmt` and `datetime_fmt` should be specified.
-    datetime_fmt : str, optional
-        String directives (strftime) to format log timestamp using `datetime`. Only one of `datefmt`
-        and `datetime_fmt` should be specified.
+        3339.
+    use_datetime: str, optional
+        Interpret `datefmt` as a format string for `datetime.datetime.strftime`, rather than
+        `time.strftime`.
+
+        See https://docs.python.org/3/library/datetime.html#strftime-strptime-behavior . This
+        also supports a custom %F directive for milliseconds.
     json_serializer : Callable, optional
         function to serialize `obj` to a JSON formatted `str`, by default json.dumps
     json_deserializer : Callable, optional

tests/functional/test_logger.py

@@ -615,12 +615,13 @@ def handler(event, context, my_custom_option=None):
 
 
 @pytest.mark.parametrize("utc", [False, True])
-def test_datetime_fmt(stdout, service_name, utc):
+def test_use_datetime(stdout, service_name, utc):
     # GIVEN
     logger = Logger(
         service=service_name,
         stream=stdout,
-        datetime_fmt="custom timestamp: milliseconds=%F microseconds=%f timezone=%z",
+        datefmt="custom timestamp: milliseconds=%F microseconds=%f timezone=%z",
+        use_datetime=True,
         utc=utc,
     )