title: Pandas cut with user-defined bins
body: <p>I am working in Python and using the cut functionality in Pandas. I would like to have the bins in my pd.cut to be based on user-defined comma separated integers, with predefined top and bottom bounds. In other words, I would like to predefine <code>bins</code> as <code>[0, 100000]</code> and then append user defined integers to this set of numbers. If the user entered <code>5, 100, 5000</code> then <code>bins</code> would become <code>[0, 5, 100, 5000, 100000]</code> and would then work with <code>pd.cut(df['Quantity'], bins</code>.</p>
  
  <p>I have tried a number of solutions with no avail up to this point - any input would be greatly appreciated!</p>