import matplotlib
matplotlib.use('TkAgg')  # same with 'agg'

import matplotlib.pyplot as plt

fig = plt.figure()
ax1 = fig.add_subplot(111)

ax2 = ax1.twinx()
ax2.remove()

ax3 = fig.add_subplot(111)
ax3.set_xlim([1, 5])

plt.show()

Traceback (most recent call last):
  File "E:\dev\prs\main\test2.py", line 13, in <module>
    ax3.set_xlim([1, 5])
  File "e:\dev\envs\py34_x86\Python\lib\site-packages\matplotlib\axes\_base.py", line 2783, in set_xlim
    other.figure.canvas is not None):
AttributeError: 'NoneType' object has no attribute 'canvas'