Add utility "setup_logging()" to setup/update logging

This "setup_logging()" utility can setup the logging module with the
given configuration dict, and can also update the logging configs by
specify the additional parameters.

1 files changed, 70 insertions, 0 deletions

diff --git a/fg21sim/utils/logging.py b/fg21sim/utils/logging.py
new file mode 100644
index 0000000..81e8880
--- /dev/null
+++ b/fg21sim/utils/logging.py
@@ -0,0 +1,70 @@
+# Copyright (c) 2016 Weitian LI <liweitianux@live.com>
+# MIT license
+
+"""
+Logging utilities.
+"""
+
+import sys
+import logging
+from logging import FileHandler, StreamHandler
+
+
+def setup_logging(dict_config=None, stream=None, logfile=None):
+    """Setup the logging.
+    This will override the logging configurations in the config file
+    if specified (e.g., by command line arguments).
+
+    Parameters
+    ----------
+    dict_config : dict
+        Dict of logging configurations specified in the config file.
+    stream : string; "stderr", "stdout", or ""
+        This controls where the log messages go to.
+        If not None, then override the old ``StreamHandler`` settings;
+        if ``stream=""``, then disable the ``StreamHandler``.
+    logfile : string
+        Specify the file where the log messages go to.
+        If ``logfile=""``, then disable the ``FileHandler``.
+
+    NOTE
+    ----
+    If the logging already has ``StreamHandler`` or ``FileHandler``
+    configured, then the old handler will be *replaced* (i.e., remove
+    the old one, then add the new one).
+    """
+    # default file open mode for logging to file
+    filemode = "a"
+    if dict_config:
+        logging.basicConfig(**dict_config)
+        filemode = dict_config["filemode"]
+    #
+    root_logger = logging.getLogger()
+    if stream in ["", "stderr", "stdout"]:
+        for handler in root_logger.handlers:
+            if isinstance(handler, StreamHandler):
+                # remove old ``StreamHandler``
+                root_logger.removeHandler(handler)
+        if stream == "":
+            # disable ``StreamHandler``
+            pass
+        else:
+            # add new ``StreamHandler``
+            handler = StreamHandler(getattr(sys, stream))
+            root_logger.addHandler(handler)
+    else:
+        raise ValueError("invalid stream: %s" % stream)
+    #
+    if logfile is not None:
+        for handler in root_logger.handlers:
+            if isinstance(handler, FileHandler):
+                filemode = handler.mode
+                # remove old ``FileHandler``
+                root_logger.removeHandler(handler)
+        if logfile == "":
+            # disable ``FileHandler``
+            pass
+        else:
+            # add new ``FileHandler``
+            handler = FileHandler(logfile, mode=filemode)
+            root_logger.addHandler(handler)