Add 'Python log to a file'

Python-log-to-a-file.md

@@ -0,0 +1,29 @@
+```
+import logging
+import traceback
+import sys
+
+# this raise an error
+
+def err():
+    raise ValueError("This is not the expected value")
+
+# configure the logger handler and formatter for the log file
+
+logger = logging.getLogger("file_logger")
+logger.setLevel(logging.DEBUG)
+fh = logging.FileHandler("python_process.log")
+fh.setLevel(logging.DEBUG)
+ff = logging.Formatter(fmt='%(asctime)s,%(msecs)d %(name)s %(levelname)s %(message)s')
+fh.setFormatter(ff)
+logger.addHandler(fh)
+
+# Log known errors to a file. Logging all possible exceptions is not recommended
+
+try:
+    err()
+except ValueError as e:
+    logger.error(str(e))
+    logger.error(traceback.format_exc())
+    logger.error(sys.exc_info()[2])
+```