title: python adding binary number
body: <p>There is an unexpected output when I am dealing with binary number in Python 3.</p>
  
  <p>We can easily convert any integer to binary by built-in bin() function. For example:</p>
  
  <pre><code>&gt;&gt;&gt;bin(4243125)
  </code></pre>
  
  <p>Here's the issue when I try to add 2 binary function:</p>
  
  <pre><code>&gt;&gt;&gt;bin(x)+bin(y)
  </code></pre>
  
  <p>The output is concatenation of two binary number, not addition of binary number. The output of binary function has become a string.</p>
  
  <p>Addition in a binary function works fine:</p>
  
  <pre><code>&gt;&gt;&gt;bin(x+y)
  </code></pre>
  
  <p>And try to add two binary number without bin() is viable too:</p>
  
  <pre><code>&gt;&gt;&gt;0b100+0b10111
  </code></pre>
  
  <p>What is the reasons/purposes of setting a bin() output to a string? </p>