title: How to add attributes to a subclass of pandas.DataFrame?
body: <p>I would like to add attributes to a subclass of DataFrame, but I get an error:</p>
  
  <pre><code>&gt;&gt;&gt; import pandas as pd
  &gt;&gt;&gt;class Foo(pd.DataFrame):
  ...     def __init__(self):
  ...         self.bar=None
  ...         
  &gt;&gt;&gt; Foo()
  
  
  RuntimeError: maximum recursion depth exceeded
  </code></pre>