Hi: I have given my students a little problem that involves producing an "animation" with each step in the animation being a PDB model within an NMR generated file. The solution to the problem is more complicated than what is shown in the script below involving as it does the calculation of RMSDs to get smoother transitions between successive displays of the models. My answer script is not working as expected due to an issue that I have recreated in a shorter script that follows next: import chimera from chimera import runCommand import time numCycles = 10 # ID's to try: 1BMR, 1DW5, 1QDP, 1D1H, 1N4N, 1IJC, 1PFD, 2LI3, 1AH1 prot_L = chimera.openModels.open("1AH1", type="PDB") numModels = len(prot_L) runCommand("~modeldisp") for ic in range(numCycles): for aix in range(numModels): subIDstr = str(prot_L[aix].subid) command = "modeldisp #0" + "." + subIDstr runCommand(command) time.sleep(0.1) command = "~modeldisp #0" + "." + subIDstr # The following print command seems to be necessary to get # the animation! print command runCommand(command) This script runs just fine and does exactly what I wanted it to do. Here is the problem: If I remove the print statement, initially there for debugging, the script does not work! It seems weird that printing the argument for the runCommand would have any effect on the execution of the runCommand statement. Am I missing some vital point here???? I am running the latest version of Chimera: (version 1.6 build 35398) under Windows 7 Professional. Prior to each run I have being doing File... Close Session to eliminate any models that were brought in on a previous run. Cheers, Forbes Burkowski