title: Python group by and find find first sequence that matches a criterion
body: <p>So I am a beginner and I found many posts about how to find first sequence hat matches a criterion but I don't know how to combine it with "group by" function and displaying it new column.</p>
  
  <p>I need to group data by column "Group" and find the first value that is >0 and show it in a now column repeatedly in every row for the group.</p>
  
  <p>Input:</p>
  
  <pre class="lang-py prettyprint-override"><code>df_input = pd.DataFrame({
      "Group": ["A", "A", "A", "A", "A", "B", "B", "B", "B", "C", "C", "C"],
      "Value": [0, 1, 0, 3, 5, 0, 2, 4, 4, 0, 3, 0]
  })
  </code></pre>
  
  <p>Output:</p>
  
  <pre class="lang-py prettyprint-override"><code>df_output = pd.DataFrame({
      "Group": ["A", "A", "A", "A", "A", "B", "B", "B", "B", "C", "C", "C"],
      "Value": [0, 1, 0, 3, 5, 0, 2, 4, 4, 0, 3, 0],
      "First sequence": [1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3]
  })
  </code></pre>