title: Renaming pandas dataframe column on copy affects the original dataframe
body: <p>I don't understand why this renaming operation affects the original dataframe when the copy command is used. Why is df_copy a view of df and not really a copy? I would expect the print statement to output 'x' not 'y'.</p>
  
  <pre><code>df = pandas.DataFrame({'x': [0, 1]})
  df_copy = df.copy(deep=True)
  df_copy.columns.values[0] = 'y'
  print(df.columns)
  </code></pre>