title: ImportError: No module named matplotlib.pyplot
body: <p>I am currently practicing matplotlib. This is the first example I practice.</p>
  
  <pre><code>#!/usr/bin/python
  
  import matplotlib.pyplot as plt
  
  radius = [1.0, 2.0, 3.0, 4.0]
  area = [3.14159, 12.56636, 28.27431, 50.26544]
  
  plt.plot(radius, area)
  plt.show()
  </code></pre>
  
  <p>When I run this script with <code>python ./plot_test.py</code>, it shows plot correctly. However, I run it by itself, <code>./plot_test.py</code>, it throws the followings:</p>
  
  <pre><code>Traceback (most recent call last):
  File "./plot_test.py", line 3, in &lt;module&gt;
    import matplotlib.pyplot as plt
  ImportError: No module named matplotlib.pyplot
  </code></pre>
  
  <p>Does python look for matplotlib in different locations?</p>
  
  <p>The environment is:</p>
  
  <pre><code>Mac OS X 10.8.4 64bit
  built-in python 2.7
  </code></pre>
  
  <p>numpy, scipy, matplotlib is installed with:</p>
  
  <pre><code>sudo port install py27-numpy py27-scipy py27-matplotlib \
  py27-ipython +notebook py27-pandas py27-sympy py27-nose
  </code></pre>