IPython/config/profile/pylab/ipython_config.py

c = get_config()

# This can be used at any point in a config file to load a sub config
# and merge it into the current one.
load_subconfig('ipython_config.py')

lines = """
import matplotlib
%gui -a wx
matplotlib.use('wxagg')
matplotlib.interactive(True)
from matplotlib import pyplot as plt
from matplotlib.pyplot import *
"""

# You have to make sure that attributes that are containers already
# exist before using them.  Simple assigning a new list will override
# all previous values.
if hasattr(c.Global, 'exec_lines'):
    c.Global.exec_lines.append(lines)
else:
    c.Global.exec_lines = [lines]