title: Python strict string replacement
body: <p>I need to replace rownum and rownum_ in &quot;My num is rownum, your is rownum_&quot; using <code>placeholderdict = {rownum:20, rownum_:25}.</code></p>
  <p>When I tried, it gets replaced like &quot;<code>My num is 20, yours is 20_</code>&quot; . Expected is &quot;<code>My num is 20, yours is 25</code>&quot;</p>
  <p>Please share some tips.</p>