title: find the first occurrence of a value (from a list of values)in a pandas dataframe and return the index of the row
body: <p>I have a pandas DataFrame (the actual data set is far larger and contains numbers from 1-50):</p>
  <pre><code>          date           main   N1  N2  N3  N4  N5
  0   2020-09-18  7-12-14-40-42   7   12  14  40  42
  1   2020-09-11  2-5-24-43-45    2   5   24  43  45
  2   2020-09-04  5-23-28-38-49   5   23  28  38  49
  3   2020-08-28  8-11-22-38-41   8   11  22  38  41
  4   2020-08-21  26-27-30-46-49  26  27  30  46  49
  </code></pre>
  <p>I want to return the row index for the first occurrence of each number. So far the only way that I have been able to achieve this is by &quot;manually&quot; using</p>
  <pre><code>lotteryData.loc[(lotteryData.N5==1)].head(49)
  </code></pre>
  <p>which in this example gives row index number 2. This is obviously very clumsy and does not take advantage of the Pandas DataFrame capability at all. Is there a way of iterating through the list in the format 5-23-28-38-49 directly to capture this information or a way to iterate through the columns to find the first occurrence of all numbers between 1 and 50</p>