fix log bevavior (#96)

Author: robinzyb

cp2kdata/log.py

@@ -1,16 +1,36 @@
 import logging
 import os
 
-level_name = os.environ.get('CP2KDATA_LOG_LEVEL', 'INFO')
+_LOGGER_NAME = "cp2kdata"
+
+level_name = os.environ.get("CP2KDATA_LOG_LEVEL", "INFO")
 level = logging._nameToLevel.get(level_name, logging.INFO)
 
 # format to include timestamp and module
-if level_name == 'DEBUG':
-    logging.basicConfig(format='CP2KDATA| %(asctime)s - %(levelname)-8s %(name)-40s: %(message)s', level=level)
+if level_name == "DEBUG":
+    _formatter = logging.Formatter(
+        "CP2KDATA| %(asctime)s - %(levelname)-8s %(name)-40s: %(message)s"
+    )
 else:
-    logging.basicConfig(format='CP2KDATA| %(message)s', level=level)
+    _formatter = logging.Formatter("CP2KDATA| %(message)s")
+
+_logger = logging.getLogger(_LOGGER_NAME)
+_logger.setLevel(level)
+_logger.propagate = True
+
+# Only attach a handler when the root logger has no handlers.
+# This keeps standalone behavior without changing global logging config.
+if not logging.getLogger().handlers and not _logger.handlers:
+    _handler = logging.StreamHandler()
+    _handler.setLevel(level)
+    _handler.setFormatter(_formatter)
+    _logger.addHandler(_handler)
+
 # suppress transitions logging
 # logging.getLogger('transitions.core').setLevel(logging.WARNING)
 
+
 def get_logger(name=None):
-    return logging.getLogger(name)
+    if name:
+        return logging.getLogger(f"{_LOGGER_NAME}.{name}")
+    return _logger