title: Change one value based on another value in pandas
body: <p>I'm trying to reproduce my Stata code in Python, and I was pointed in the direction of Pandas.  I am, however, having a hard time wrapping my head around how to process the data.</p>
  <p>Let's say I want to iterate over all values in the column head 'ID.' If that ID matches a specific number, then I want to change two corresponding values FirstName and LastName.</p>
  <p>In Stata it looks like this:</p>
  <pre><code>replace FirstName = &quot;Matt&quot; if ID==103
  replace LastName =  &quot;Jones&quot; if ID==103
  </code></pre>
  <p>So this replaces all values in FirstName that correspond with values of ID == 103 to Matt.</p>
  <p>In Pandas, I'm trying something like this</p>
  <pre><code>df = read_csv(&quot;test.csv&quot;)
  for i in df['ID']:
      if i ==103:
            ...
  </code></pre>
  <p>Not sure where to go from here.  Any ideas?</p>