diff --git a/tools/pylibopenflow/pylib/output.py b/tools/pylibopenflow/pylib/output.py
new file mode 100644
index 0000000..64df4f5
--- /dev/null
+++ b/tools/pylibopenflow/pylib/output.py
@@ -0,0 +1,85 @@
+"""This module implements output printing.
+
+Output are divided into 4 levels and
+can be configured for different verbosity
+
+Copyright(C) 2009, Stanford University
+Date August 2009
+Created by ykk
+"""
+
+##Various output modes
+MODE = {}
+MODE["ERR"] = 0
+MODE["WARN"] = 1
+MODE["INFO"] = 2
+MODE["DBG"] = 3
+
+#Global mode
+global output_mode
+output_mode = None
+
+def set_mode(msg_mode, who=None):
+    """Set the message mode for who
+    If who is None, set global mode
+    """
+    global output_mode
+    if (output_mode == None):
+        output_mode = {}
+        output_mode["global"] = MODE["WARN"]
+        output_mode["DBG"] = []
+        output_mode["INFO"] = []
+        output_mode["WARN"] = []
+
+    #Set global mode
+    if (who == None):
+        output_mode["global"] = MODE[msg_mode]
+        return
+    
+    #Individual mode
+    if (msg_mode == "ERR"):
+        return
+    for mode in ["WARN","INFO","DBG"]:
+        if (not (who in mode[mode])):
+            mode[mode].append(who)
+        if (msg_mode == mode):
+            return
+    
+def output(msg_mode, msg, who=None):
+    """Print message
+    """
+    global output_mode
+    if (output_mode == None):
+        raise RuntimeException("Output mode is not set")
+
+    #Indicate who string
+    if (who == None):
+        whostr = ""
+    else:
+        whostr = who+":"
+
+    #Print output 
+    if (MODE[msg_mode] <= output_mode["global"]):
+        print msg_mode.ljust(4, ' ')+"|"+whostr+msg
+    elif (who in output_mode[msg_mode]):
+        print msg_mode.ljust(4, ' ')+"|"+whostr+msg
+        
+def err(msg, who=None):
+    """Print error messages
+    """
+    output("ERR", msg, who)
+
+def warn(msg, who=None):
+    """Print warning messages
+    """
+    output("WARN", msg, who)
+
+def info(msg, who=None):
+    """Print informational messages
+    """
+    output("INFO", msg, who)
+
+def dbg(msg, who=None):
+    """Print debug messages
+    """
+    output("DBG", msg, who)