save_state method, safer logging

Call save_state to dump the current attributes of the XFaster object to disk.
Useful for debugging.

xfaster/xfaster_class.py

@@ -437,7 +437,7 @@ def root_notice(msg, *args, **kwargs):
         handler.setFormatter(fmt)
 
         # configure logger
-        self.logger = logging.getLogger("xfaster")
+        self.logger = logging.getLogger("xfaster.{}".format(id(self)))
         # replace any existing handlers before adding one
         if self.logger.hasHandlers():
             for h in list(self.logger.handlers):
@@ -488,7 +488,7 @@ def __del__(self):
         """
 
         # cleanup logging handlers
-        for handler in self.logger.handlers[::-1]:
+        for handler in list(self.logger.handlers[::-1]):
             try:
                 handler.acquire()
                 handler.flush()
@@ -497,6 +497,7 @@ def __del__(self):
                 pass
             finally:
                 handler.release()
+            self.logger.removeHandler(handler)
 
     def _get_data_files(
         self,
@@ -1658,6 +1659,31 @@ def save_data(self, name, from_attrs=[], file_attrs=[], **data):
         data["output_file"] = output_file
         return data
 
+    def save_state(self, tag):
+        """
+        Save current object state to disk.
+
+        Arguments
+        ---------
+        tag : str
+            Set the name for the output file to ``state_<tag>``.  Otherwise the
+            standard file options are applied to produce the output filename.
+            See ``get_filename`` for details.
+        """
+        data = vars(self)
+        data["data_version"] = self.data_version
+        data.pop("logger")
+
+        file_opts = {}
+        for opt in ["map_tag", "iter_index", "data_opts", "bp_opts", "extra_tag"]:
+            if opt in data:
+                file_opts[opt] = data[opt]
+
+        name = "state_{}".format(tag)
+        output_file = self.get_filename(name, ext=".npz", **file_opts)
+
+        pt.save(output_file, **data)
+
     def save_config(self, cfg):
         """
         Save a configuration file for the current run on disk.