Вот решение, которое показывает два возможных способа решения вашей проблемы:
import matplotlib.pyplot as plt
from mpl_toolkits.axes_grid.axislines import Subplot
left,bottom,width,height= -0.02 , 0.12, 1, 0.9
fig = plt.figure(figsize=(3,5))
ax1 = plt.Axes(fig,[left,bottom,width,height])
ax1.plot([1,2,3,4],'b') # plot on the first axes you created
fig.add_axes(ax1)
# using subplot you are acually using higher level objects
ax2 = Subplot(fig,111) # this addes another axis instance
fig.add_subplot(ax2)
ax2.axis["top"].set_visible(False)
ax2.axis["right"].set_visible(False)
ax2.plot([1,2,3,4,5],'r') # thos plots on the second
# now comment everything in ax2, and uncomment ax3
# you will get a crude, low level control of axes
# but both do what you want...
#ax3 = plt.Axes(fig,[left+0.2,bottom-0.2,width,height])
#ax3.plot([1,2,3,4],'g') # plot on the first axes you created
#for loc, spine in ax3.spines.iteritems():
# if loc in ['left','bottom']:
# spine.set_position(('outward',10)) # outward by 10 points
# if loc in ['right','top']:
# spine.set_color('none') # don't draw spine
#fig.add_axes(ax3)
plt.show()