title: python dataclass no attribute post_init
body: <p>When I run the code below:</p>
  <pre><code>import pandas as pd
  from dataclasses import dataclass
  
  
  @dataclass
  class SomeClass:
      df_in: pd.DataFrame
  
      def __post__init__(self):
          self.b = 1
  
  
  if __name__ == '__main__':
      df_in = pd.DataFrame([])
      p = SomeClass(df_in=df_in)
      p.b
  </code></pre>
  <p>I get</p>
  <pre><code>AttributeError: 'SomeClass' object has no attribute 'b'
  </code></pre>
  <p>Why?</p>
  <p>EDIT:</p>
  <p>Am I using <strong>post__init</strong> correctly as there is no <strong>init</strong> in dataclasses</p>