Solution to Indented List Problem

This post originally appeared on the Software Carpentry website.

Last week's homework was to convert a two-level bullet-point list like this:

* A
* B
  * 1
  * 2
* C
  * 3

into an HTML list like this:

<ul>
  <li>A</li>
  <li>B
    <ul>
      <li>1</li>
      <li>2</li>
    </ul>
  </li>
  <li>C
    <ul>
      <li>3</li>
    </ul>
  </li>
</ul>

so it would display like this:

• A
• B
  • 1
  • 2
• C
  • 3

My solution is shown in the video below; the code follows.

import sys

def do_inner(lines, current):
    need_to_start = True
    need_to_close = False
    while (current < len(lines)) and \
          lines[current].startswith('  * '):
        if need_to_start:
            print '  <ul>'
            need_to_start = False
        text = lines[current].lstrip('  * ').rstrip()
        print '  <li>' + text + '</li>'
        need_to_close = True
        current += 1
    if need_to_close:
        print '  </ul>'
    return current

def do_outer(lines):
    print '<ul>'
    current = 0
    while current < len(lines):
        assert lines[current].startswith('* ')
        text = lines[current].lstrip('* ').rstrip()
        print '<li>' + text
        current = do_inner(lines, current+1)
        print '</li>'
    print '</ul>'

lines = sys.stdin.readlines()
do_outer(lines)