title: What does the 1 in match.group(1) mean?
body: <p>I met the codes here:</p>
  <pre><code>&gt;&gt;&gt; import urllib, re
  &gt;&gt;&gt; prefix = &quot;http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing=&quot;
  &gt;&gt;&gt; findnothing = re.compile(r&quot;nothing is (\d+)&quot;).search
  &gt;&gt;&gt; nothing = '12345'
  &gt;&gt;&gt; while True:
  ...     text = urllib.urlopen(prefix + nothing).read()
  ...     print text
  ...     match = findnothing(text)
  ...     if match:
  ...         nothing = match.group(1)
  ...         print &quot;   going to&quot;, nothing
  ...     else:
  ...         break
  </code></pre>
  <p>What does the <code>1</code> in <code>match.group(1)</code> mean?</p>