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user_id=80475

To clarify, the private variables are just a way to move the
defaults  out of the class definition and give the OP more
control over formatting:

_legend = """
<table summary="Legends" style="font-family:Courier">
    <tr> <th colspan="2"> Legends </th> </tr>
    <tr> <td> <table border="" summary="Colors">
                  <tr><th> Colors </th> </tr>
                  <tr><td
class="diff_add"> Added </td></tr>
                  <tr><td class="diff_chg">Changed</td> </tr>
                  <tr><td class="diff_sub">Deleted</td> </tr>
              </table></td>
         <td> <table border="" summary="Links">
                  <tr><th colspan="2"> Links </th> </tr>
                  <tr><td>(f)irst change</td> </tr>
                  <tr><td>(n)ext change</td> </tr>
                  <tr><td>(t)op</td> </tr>
              </table></td> </tr>
</table>
"""

class HtmlDiff(object):

    file_template = _file_template
    styles = _styles
    linenum_template = _linenum_template
    table_template = _table_template
    legend = _legend

    def __init__(self,prefix=['from','to'], linejunk=None,
      .  .  .