#8040: add a version switcher to the documentation. Patch by Yury Selivanov.

Doc/tools/sphinxext/layout.html

@@ -3,18 +3,26 @@
         <li><img src="{{ pathto('_static/py.png', 1) }}" alt=""
                  style="vertical-align: middle; margin-top: -1px"/></li>
         <li><a href="http://www.python.org/">Python</a>{{ reldelim1 }}</li>
-        <li><a href="{{ pathto('index') }}">{{ shorttitle }}</a>{{ reldelim1 }}</li>
+        <li>
+          {%- if versionswitcher is defined %}
+          <span class="version_switcher_placeholder">{{ release }}</span>
+          <a href="{{ pathto('index') }}">Documentation</a>{{ reldelim1 }}
+          {%- else %}
+          <a href="{{ pathto('index') }}">{{ shorttitle }}</a>{{ reldelim1 }}
+          {%- endif %}
+        </li>
 {% endblock %}
 {% block extrahead %}
     <link rel="shortcut icon" type="image/png" href="{{ pathto('_static/py.png', 1) }}" />
     {% if not embedded %}<script type="text/javascript" src="{{ pathto('_static/copybutton.js', 1) }}"></script>{% endif %}
+    {% if versionswitcher is defined and not embedded %}<script type="text/javascript" src="{{ pathto('_static/version_switch.js', 1) }}"></script>{% endif %}
 {{ super() }}
 {% endblock %}
 {% block footer %}
     <div class="footer">
     &copy; <a href="{{ pathto('copyright') }}">Copyright</a> {{ copyright|e }}.
     <br />
-    The Python Software Foundation is a non-profit corporation.  
+    The Python Software Foundation is a non-profit corporation.
     <a href="http://www.python.org/psf/donations/">Please donate.</a>
     <br />
     Last updated on {{ last_updated|e }}.

Doc/tools/sphinxext/static/version_switch.js

+(function() {
+  'use strict';
+
+  var all_versions = {
+    '3.4': 'dev (3.4)',
+    '3.3': '3.3',
+    '3.2': '3.2',
+    '2.7': '2.7',
+    '2.6': '2.6'
+  };
+
+  function build_select(current_version, current_release) {
+    var buf = ['<select>'];
+
+    $.each(all_versions, function(version, title) {
+      buf.push('<option value="' + version + '"');
+      if (version == current_version)
+        buf.push(' selected="selected">' + current_release + '</option>');
+      else
+        buf.push('>' + title + '</option>');
+    });
+
+    buf.push('</select>');
+    return buf.join('');
+  }
+
+  function patch_url(url, new_version) {
+    var url_re = /\.org\/(\d|py3k|dev|((release\/)?\d\.\d[\w\d\.]*))\//,
+        new_url = url.replace(url_re, '.org/' + new_version + '/');
+
+    if (new_url == url && !new_url.match(url_re)) {
+      // python 2 url without version?
+      new_url = url.replace(/\.org\//, '.org/' + new_version + '/');
+    }
+    return new_url;
+  }
+
+  function on_switch() {
+    var selected = $(this).children('option:selected').attr('value');
+
+    var url = window.location.href,
+        new_url = patch_url(url, selected);
+
+    if (new_url != url) {
+      // check beforehand if url exists, else redirect to version's start page
+      $.get(new_url, function() {
+        window.location.href = new_url;
+      }).error(function() {
+        window.location.href = 'http://docs.python.org/' + selected;
+      });
+    }
+  }
+
+  $(document).ready(function() {
+    var select = build_select(DOCUMENTATION_OPTIONS.VERSION,
+                              DOCUMENTATION_OPTIONS.RELEASE);
+    $('.version_switcher_placeholder').html(select);
+    $('.version_switcher_placeholder select').bind('change', on_switch);
+  });
+})();

Misc/NEWS

@@ -636,6 +636,9 @@ Build
 Documentation
 -------------
 
+- Issue #8040: added a version switcher to the documentation.  Patch by
+  Yury Selivanov.
+
 - Issue #16115: Improve subprocess.Popen() documentation around args, shell,
   and executable arguments.