title: Python 2.7 int(str, base) confusion
body: <p>I am trying to use the int(x,  base) class functionality using Python 2.7</p>
  
  <p>when I do:
  <code>num = int('100', 2)</code> 
  I receive the answer 4</p>
  
  <p>however, when I do <code>num = int('72', 2)</code> I get the following traceback. </p>
  
  <pre><code>Traceback (most recent call last):
    File "foobar1.py", line 26, in &lt;module&gt;
      num = int('72', 4)
  ValueError: invalid literal for int() with base 4: '72'
  </code></pre>
  
  <p>I'm not sure what I'm missing.  </p>