>>> """
===============================
Legend using pre-defined labels
===============================

Defining legend labels with plots.
"""
... 
... 
... import numpy as np
... import matplotlib.pyplot as plt
... 
... # Make some fake data.
... a = b = np.arange(0, 3, .02)
... c = np.exp(a)
... d = c[::-1]
... 
... # Create plots with pre-defined labels.
... fig, ax = plt.subplots()
... ax.plot(a, c, 'k--', label='Model length')
... ax.plot(a, d, 'k:', label='Data length')
... ax.plot(a, c + d, 'k', label='Total message length')
... 
... legend = ax.legend(loc='upper center', shadow=True, fontsize='x-large')
... 
... # Put a nicer background color on the legend.
... legend.get_frame().set_facecolor('C0')
... 
... plt.show()
... 
... #############################################################################
... #
... # .. admonition:: References
... #
... #    The use of the following functions, methods, classes and modules is shown
... #    in this example:
... #
... #    - `matplotlib.axes.Axes.plot` / `matplotlib.pyplot.plot`
... #    - `matplotlib.axes.Axes.legend` / `matplotlib.pyplot.legend`
...