WyPy

While googling for an entirely different thing, I found WyPy, a minimal Wiki written in just 23 lines of Python for the ShortestWikiContest:

#!/usr/bin/python
import re, os, os.path, cgi, popen2; env, ex = os.getenv, os.path.exists
def load(n): return (ex('w/'+n) and open('w/'+n).read()) or ''
def fs(s): return reduce(lambda s, r: re.sub('(?m)'+r[0], r[1], s), (('\r',''),
   ('(^|[^A-Za-z0-9?])(([A-Z][a-z]+){2,})', lambda m: (m.group(1) + '%s&lt;a hr' \
    'ef=wypy?%s'+m.group(2)+'%s&gt;%s&lt;/a&gt;') % ((m.group(2),'p=','&amp;amp;q=e','?'),
   ('','','',m.group(2)))[ex('w/'+m.group(2))]),  ('^\{\{$','\n&lt;ul&gt;'),
   ('^\* ','&lt;li&gt;'),  ('^}}$','&lt;/ul&gt;'),  ('^---$','&lt;hr&gt;'),  ('\n\n','&lt;p&gt;'),
   ('(ht|f)tp:[^&lt;&gt;"\s]+','&lt;a href="\g&lt;0&gt;"&gt;\g&lt;0&gt;&lt;/a&gt;')), cgi.escape(s))
def do(m, n): return {'get':'&lt;h1&gt;WyPy:&lt;a href=wypy?p=%s&amp;amp;q=f&gt;%s&lt;/a&gt;&lt;/h1&gt;(' \
   '&lt;a href=wypy?p=%s&amp;amp;q=e&gt;edit me&lt;/a&gt;)&lt;p&gt;%s' % (n, n, n, fs(load(n)) or n),
   'edit': '&lt;form action=wypy?%s method=POST&gt;&lt;h1&gt;%s&lt;input type=hidden name=p' \
   ' value=%s&gt; &lt;input type=submit&gt;&lt;/h1&gt;&lt;textarea name=t rows=15 cols=80&gt;%s&lt;/' \
   'textarea&gt;&lt;/form&gt;' % (n, fs(n), n, load(n) or "Describe %s" % n), 'find':
   ('&lt;h1&gt;Links: %s&lt;/h1&gt;' % fs(n))+fs('{{\n* %s\n}}' % '\n* '.join(filter(
    lambda s: open('w/'+s).read().find(n) &gt; -1, os.listdir('w'))))}.get(m)
def main(f):
   n = f.get('p') or env("QUERY_STRING") or ''; n = ('HomePage',n)[n.isalpha()]
   print "Content-type: text/html; charset=utf-8\r\n\r\n&lt;title&gt;%s&lt;/title&gt;" % n
   if env("REQUEST_METHOD") == "POST": open('w/'+n, 'w').write(f['t'])
   print do({'e':'edit', 'f':'find'}.get(f.get('q')) or 'get', n)
if __name__=="__main__":
   main(dict([(i.name, i.value) for i in cgi.FieldStorage().list]))