title: python Pandas optimization for ubyte data (0..255)
body: <p>How is it possible to optimize Pandas df to ubyte data type (0..255)? (by default is int64 for integer)</p>
  <p>If I will convert data to Categorical type, will df use less memory?</p>
  <p>Or the only way to optimize it - use NumPy instead of Pandas?</p>