Editing Practical Pymol for Beginners (section)

====Introduction and Very Simple Scripting====
Scripting in PyMOL ranges from very simple to very intricate.  You can make a simple loop (say rotating a molecule one-degree at a time) or execute full featured scripts.  Once you've got the basics of PyMOL down, learning scripting will greatly enhance your productivity and capabilities.

Because of the way PyMOL is built on top of the Python interpreter, any command that PyMOL doesn't recognize it passes on to Python to execute.  This is a '''very''' handy feature--you essentially have a live Python interpreter you can interact with, which makes your life much easier.  Take the following for example:
<source lang="python">
f = 10.
for x in range(0,100,10):
  cmd.set("spec_direct_power", float(float(x) / f))
  cmd.png("spec_dir_power" + str(x) + ".png", ray=1)
</source>

This simple script of 4 lines will create 10 images each one with the [[Spec_direct_power]] changed (see the [[Spec_direct_power]] for the output of this script; the animated GIF).  Did you notice that '''f''' on line 1 and '''for''' and '''x''' on line 2 are not PyMOL commands or symbols?  You can simply write Python code that interacts with PyMOL.  Brilliant!