title: How to give column name for groupby value in PYTHON
body: <p>My dataset:</p>
  
  <pre><code> - City_name
   - mumbai
   - kolkata
   - mangalore
   - mumbai
   - mumbai
   - kolkata
  </code></pre>
  
  <p>My code:</p>
  
  <pre><code>tot=data.groupby('City_name').size()
  </code></pre>
  
  <p>What I got:</p>
  
  <pre><code> - City_name
   - kolkata        2
   - mangalore      1
   - mumbai         3
  </code></pre>
  
  <p>What I want:</p>
  
  <pre><code> - City_name     Thefts
   - kolkata         2
   - mangalore     - 1
   - mumbai        - 3
  </code></pre>