diff --git a/src/python/oftest/__init__.py b/src/python/oftest/__init__.py
index 9199b1a..c78bb67 100644
--- a/src/python/oftest/__init__.py
+++ b/src/python/oftest/__init__.py
@@ -1,5 +1,7 @@
 '''Docstring to silence pylint; ignores --ignore option for __init__.py'''
 import sys
+import os
+import logging
 
 # Global config dictionary
 # Populated by oft.
@@ -8,3 +10,31 @@
 # Global DataPlane instance used by all tests.
 # Populated by oft.
 dataplane_instance = None
+
+def open_logfile(name):
+    """
+    (Re)open logfile
+
+    When using a log directory a new logfile is created for each test. The same
+    code is used to implement a single logfile in the absence of --log-dir.
+    """
+
+    _format = "%(asctime)s.%(msecs)03d  %(name)-10s: %(levelname)-8s: %(message)s"
+    _datefmt = "%H:%M:%S"
+
+    if config["log_dir"] != None:
+        filename = os.path.join(config["log_dir"], name) + ".log"
+    else:
+        filename = config["log_file"]
+
+    logger = logging.getLogger()
+
+    # Remove any existing handlers
+    for handler in logger.handlers:
+        logger.removeHandler(handler)
+        handler.close()
+
+    # Add a new handler
+    handler = logging.FileHandler(filename, mode='a')
+    handler.setFormatter(logging.Formatter(_format, _datefmt))
+    logger.addHandler(handler)