One useful feature of Chameleon is that the Python scripts that you write for your VMD files can reference external Python modules. This enables you to use the same code in multiple VMD files and Iguana channels without having to create multiple copies of it.

For example, the following Python module provides the functions you will need to detect when an idle channel has restarted:

import os
import stat
import time

def startInactivityChecking():
	global Timestamp
	try:
		Timestamp
	except NameError:
		Timestamp = time.time()

def checkForInactivity(InactivityTime):
    global Timestamp
    CurrentTime = time.time()
    Delta = int(CurrentTime - Timestamp)
    if Delta > InactivityTime:
       # print warning message - channel has restarted
       LastString = time.strftime( '%Y-%m-%d %H:%M', time.localtime(Timestamp))
       print "IDLE CHANNEL RESTARTED: first message since %s" % LastString
    # update timestamp to the time that this message came through
    Timestamp = CurrentTime

To use this Python code, you must:

• Save this code in a file on your system named inactivechannel.py;
• Ensure that Chameleon can find this file when it is searching for Python modules (see Searching for Modules for details on how to do this);
• In your VMD file, write Python scripts that refer to the module defined by this file.

In the following section, you will create a VMD file that refers to this Python code. To get a copy of the Python module, follow this link: inactivechannel.py.

	It is important to note that the name of the file is significant. In Python, the name of a module is the same as the name of the file in which it is contained. In addition, all modules must have a file suffix of .py. For example, if your file is named mymodulename.py, your Python scripts will use one of the following statements to import the module: import mymodulename from mymodulename import * For more information on importing Python modules, see Importing Modules.

	This script works only if at least one message has been sent through this channel. If the channel has never been active, and a message appears after a long initial idle period, this warning is not generated. If you need to detect that a channel has remained idle after startup, create a channel inactivity rule. See Creating a Channel Inactivity Rule for details.