4.3. SIMULATING DISCRETE-TIME MODELS WITH ONE VARIABLE 43 Code 4.7: from pylab import And then you can add the following lines to the end of your code: Code 4.8: plot (result) show) The completed code as a whole is as follows (you can download the actual Python code by clicking on the name of the code in this textbook): Code 4.9: exponential-growth.py from pylab import * a = 1.1 def initialize(): global x, result x = 1. result - [x] def observe(): global x, result result.append(x) def update(): global x, result x = a + x initialize() for t in xrange (30) update() observe() plot (result) show() Please explain what this code does in detail. It Supposed to model exponential growth is (