Adding Formatter and example including timestamp

adafruit_logging.py

@@ -64,7 +64,7 @@
 
 try:
     # pylint: disable=deprecated-class
-    from typing import Optional, Hashable
+    from typing import Optional, Hashable, Dict
     from typing_extensions import Protocol
 
     class WriteableStream(Protocol):
@@ -148,12 +148,85 @@ def _logRecordFactory(name, level, msg, args):
     return LogRecord(name, level, _level_for(level), msg, time.monotonic(), args)
 
 
+class Formatter:
+    """
+    Responsible for converting a LogRecord to an output string to be
+    interpreted by a human or external system.
+
+    Only implements a sub-set of CPython logging.Formatter behavior,
+    but retains all the same arguments in order to match the API.
+
+    The only init arguments currently supported are: fmt, defaults and
+    style. All others are currently ignored
+
+    The only two styles currently supported are '%' and '{'. The default
+    style is '{'
+    """
+
+    def __init__(  # pylint: disable=too-many-arguments
+        self,
+        fmt: Optional[str] = None,
+        datefmt: Optional[str] = None,
+        style: str = "%",
+        validate: bool = True,
+        defaults: Dict = None,
+    ):
+        self.fmt = fmt
+        self.datefmt = datefmt
+        self.style = style
+        if self.style not in ("{", "%"):
+            raise ValueError(
+                "Only '%' and '{' formatting style are supported at this time."
+            )
+
+        self.validate = validate
+        self.defaults = defaults
+
+    def format(self, record: LogRecord) -> str:
+        """
+        Format the given LogRecord into an output string
+        """
+        if self.fmt is None:
+            return record.msg
+
+        vals = {
+            "name": record.name,
+            "levelno": record.levelno,
+            "levelname": record.levelname,
+            "message": record.msg,
+            "created": record.created,
+            "args": record.args,
+        }
+        if "{asctime}" in self.fmt or "%(asctime)s" in self.fmt:
+            now = time.localtime()
+            # pylint: disable=line-too-long
+            vals[
+                "asctime"
+            ] = f"{now.tm_year}-{now.tm_mon:02d}-{now.tm_mday:02d} {now.tm_hour:02d}:{now.tm_min:02d}:{now.tm_sec:02d}"
+
+        if self.defaults:
+            for key, val in self.defaults.items():
+                if key not in vals:
+                    vals[key] = val
+
+        if self.style not in ("{", "%"):
+            raise ValueError(
+                "Only '%' and '{' formatting style are supported at this time."
+            )
+
+        if self.style == "%":
+            return self.fmt % vals
+
+        return self.fmt.format(**vals)
+
+
 class Handler:
     """Base logging message handler."""
 
     def __init__(self, level: int = NOTSET) -> None:
         """Create Handler instance"""
         self.level = level
+        self.formatter = None
 
     def setLevel(self, level: int) -> None:
         """
@@ -167,7 +240,8 @@ def format(self, record: LogRecord) -> str:
 
         :param record: The record (message object) to be logged
         """
-
+        if self.formatter:
+            return self.formatter.format(record)
         return f"{record.created:<0.3f}: {record.levelname} - {record.msg}"
 
     def emit(self, record: LogRecord) -> None:
@@ -182,6 +256,12 @@ def emit(self, record: LogRecord) -> None:
     def flush(self) -> None:
         """Placeholder for flush function in subclasses."""
 
+    def setFormatter(self, formatter: Formatter) -> None:
+        """
+        Set the Formatter to be used by this Handler.
+        """
+        self.formatter = formatter
+
 
 #  pylint: disable=too-few-public-methods
 class StreamHandler(Handler):

examples/logging_formatter_example.py

@@ -0,0 +1,48 @@
+# SPDX-FileCopyrightText: 2024 Tim Cocks
+# SPDX-License-Identifier: MIT
+
+
+"""Illustrate usage of default and custom Formatters including
+one with timestamps."""
+
+import adafruit_logging as logging
+
+# To test on CPython, un-comment below and comment out above
+# import logging
+
+
+logger = logging.getLogger("example")
+logger.setLevel(logging.INFO)
+print_handler = logging.StreamHandler()
+logger.addHandler(print_handler)
+
+default_formatter = logging.Formatter()
+
+print_handler.setFormatter(default_formatter)
+logger.info("Default formatter example")
+
+
+timestamp_formatter = logging.Formatter(fmt="%(asctime)s %(levelname)s: %(message)s")
+print_handler.setFormatter(timestamp_formatter)
+logger.info("Timestamp formatter example")
+
+
+custom_vals_formatter = logging.Formatter(
+    fmt="%(ip)s %(levelname)s: %(message)s", defaults={"ip": "192.168.1.188"}
+)
+print_handler.setFormatter(custom_vals_formatter)
+logger.info("Custom formatter example")
+
+
+bracket_timestamp_formatter = logging.Formatter(
+    fmt="{asctime} {levelname}: {message}", style="{"
+)
+print_handler.setFormatter(bracket_timestamp_formatter)
+logger.info("Timestamp formatter bracket style example")
+
+
+bracket_custom_vals_formatter = logging.Formatter(
+    fmt="{ip} {levelname}: {message}", style="{", defaults={"ip": "192.168.1.188"}
+)
+print_handler.setFormatter(bracket_custom_vals_formatter)
+logger.info("Custom formatter bracket style example")