Till now, we have used the pyplot module of matplotlib. This module makes it easy for us to use the most important plot commands directly. Mostly, we are interested in creating a figure and display it immediately. Sometimes, though, we want to generate a figure that should be modified later by changing some of its attributes. This requires us to work with graphical objects in an object-oriented way. In this section, we will present some basic steps to modify figures. For a more sophisticated object oriented approach to plotting in Python, you have to leave pyplot and have to dive directly into matplotlib with its extensive documentation.
When creating a plot that should be modified later, we need references to a figure and an axes object. For this we have to create a figure first and then define some axes and their location in the figure. And we should not forget to assign these objects to a variable:
fig = figure() ax = subplot(111)
A figure can have...