>>> r"""
================
Nested GridSpecs
================

This example demonstrates the use of nested `.GridSpec`\s.
"""
... 
... import matplotlib.pyplot as plt
... import numpy as np
... 
... 
... def squiggle_xy(a, b, c, d):
...     i = np.arange(0.0, 2*np.pi, 0.05)
...     return np.sin(i*a)*np.cos(i*b), np.sin(i*c)*np.cos(i*d)
... 
... 
... fig = plt.figure(figsize=(8, 8))
... outer_grid = fig.add_gridspec(4, 4, wspace=0, hspace=0)
... 
... for a in range(4):
...     for b in range(4):
...         # gridspec inside gridspec
...         inner_grid = outer_grid[a, b].subgridspec(3, 3, wspace=0, hspace=0)
...         axs = inner_grid.subplots()  # Create all subplots for the inner grid.
...         for (c, d), ax in np.ndenumerate(axs):
...             ax.plot(*squiggle_xy(a + 1, b + 1, c + 1, d + 1))
...             ax.set(xticks=[], yticks=[])
... 
... # show only the outside spines
... for ax in fig.get_axes():
...     ss = ax.get_subplotspec()
...     ax.spines.top.set_visible(ss.is_first_row())
...     ax.spines.bottom.set_visible(ss.is_last_row())
...     ax.spines.left.set_visible(ss.is_first_col())
...     ax.spines.right.set_visible(ss.is_last_col())
... 
... plt.show()
...