Add FileHandler class

adafruit_logging/extensions.py

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+# SPDX-FileCopyrightText: 2021 Alec Delaney for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
+"""
+`extensions`
+====================================================
+
+CircuitPython logging extension for logging to files
+
+* Author(s): Alec Delaney
+"""
+
+from . import LoggingHandler
+
+
+class FileHandler(LoggingHandler):
+    """File handler for working with log files off of the microcontroller (like
+    an SD card)
+
+    :param filepath: The filepath to the log file
+    :param mode: Whether to write ('w') or append ('a'); default is to append
+    """
+
+    def __init__(self, filepath: str, mode: str = "a"):
+        self.logfile = open(filepath, mode, encoding="utf-8")
+
+    def close(self):
+        """Closes the file"""
+        self.logfile.close()
+
+    def format(self, level: int, msg: str):
+        """Generate a string to log
+
+        :param level: The level of the message
+        :param msg: The message to format
+        """
+        return super().format(level, msg) + "\r\n"
+
+    def emit(self, level: int, msg: str):
+        """Generate the message and write it to the UART.
+
+        :param level: The level of the message
+        :param msg: The message to log
+        """
+        self.logfile.write(self.format(level, msg))

examples/logging_filehandler.py

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+# SPDX-FileCopyrightText: 2021 Alec Delaney
+# SPDX-License-Identifier: MIT
+
+import board
+import busio
+from digitalio import DigitalInOut
+import storage
+import adafruit_sdcard
+import adafruit_logging as logging
+from adafruit_logging.extensions import FileHandler
+
+# Get chip select pin depending on the board, this one is for the Feather M4 Express
+sd_cs = board.D10
+
+# Set up an SD card to write to
+spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
+cs = DigitalInOut(sd_cs)
+sdcard = adafruit_sdcard.SDCard(spi, cs)
+vfs = storage.VfsFat(sdcard)
+storage.mount(vfs, "/sd")
+
+# Initialize log functionality
+log_filepath = "/sd/testlog.log"
+logger = logging.getLogger("testlog")
+file_handler = FileHandler(log_filepath)
+logger.addHandler(file_handler)
+logger.setLevel(logging.INFO)
+
+logger.info("Logger initialized!")
+logger.debug("You can even add debug statements to the log!")