import matplotlib.pyplot as plt
 ...
 plt.semilogy(x, y)
 plt.show()

sudo port install py25-matplotlib +cairo+gtk2
sudo port install py26-matplotlib +cairo+gtk2

sudo port install py34-matplotlib +cairo+gtk2

Backend GTKCairo is interactive backend. Turning interactive mode on.
Failed to enable GUI event loop integration for 'gtk'
Traceback (most recent call last):
  File "/Applications/PyCharm CE.app/Contents/helpers/pydev/pydev_console_utils.py", line 498, in do_enable_gui
enable_gui(guiname)
  File "/Applications/PyCharm CE.app/Contents/helpers/pydev/pydev_ipython/inputhook.py", line 479, in enable_gui
return gui_hook(app)
  File "/Applications/PyCharm CE.app/Contents/helpers/pydev/pydev_ipython/inputhook.py", line 227, in enable_gtk
from pydev_ipython.inputhookgtk import create_inputhook_gtk
  File "/Applications/PyCharm CE.app/Contents/helpers/pydev/pydev_import_hook.py", line 21, in do_import
module = self._system_import(name, *args, **kwargs)
  File "/Applications/PyCharm CE.app/Contents/helpers/pydev/pydev_ipython/inputhookgtk.py", line 19, in <module>
import gtk, gobject
  File "/Applications/PyCharm CE.app/Contents/helpers/pydev/pydev_import_hook.py", line 21, in do_import
module = self._system_import(name, *args, **kwargs)
ImportError: No module named 'gtk'

import matplotlib.pyplot as plt

import matplotlib
matplotlib.use('TkAgg')
import matplotlib.pyplot as plt

condo update conda
conda install matplotlib
conda install pyqt

%matplotlib auto