title: Best way to replace `None` values with 0 in a dictionary
body: <p>I have a dictionary -</p>
  <pre><code>{
  
      'buy': {'trade_transaction_amount__sum': None, 'tax__sum': None, 'trade_fee__sum': None}, 
      'sell': {'trade_transaction_amount__sum': None, 'tax__sum': None, 'trade_fee__sum': None}
  }
  </code></pre>
  <p>What would be the best approach to replace the <code>None</code> values with <code>0</code>.</p>
  <p>Note - Not every time the values for these keys are <code>None</code>.</p>