Mako 下面开发时候，遇到这个问题
TypeError: sequence item : expected string or Unicode, long found
Trace 的情况大概这样（我的错误信息无法再现，这是某位外国友人的错误信息）
File ‘/Users/amaslov/Projects/dou-pylons/doupy/doupy/controllers/ root.py’, line 239 in staticpage
return render(’/pages/%s.html’ % name)
File ‘/Users/amaslov/Projects/dou-pylons/py/lib/python2.5/site- packages/Pylons-0.9.7-py2.5.egg/pylons/templating.py’, line 274 in render_mako
cache_type=cache_type, cache_expire=cache_expire)
File ‘/Users/amaslov/Projects/dou-pylons/py/lib/python2.5/site- packages/Pylons-0.9.7-py2.5.egg/pylons/templating.py’, line 249 in cached_template
return render_func()
File ‘/Users/amaslov/Projects/dou-pylons/py/lib/python2.5/site- packages/Pylons-0.9.7-py2.5.egg/pylons/templating.py’, line 271 in render_template
return literal(template.render_unicode(**globs))
File ‘/Users/amaslov/Projects/dou-pylons/py/lib/python2.5/site- packages/Mako-0.2.4-py2.5.egg/mako/template.py’, line 138 in render_unicode return runtime.render(self, self.callable, args, data, as_unicode=True) File ‘/Users/amaslov/Projects/dou-pylons/py/lib/python2.5/site- packages/Mako-0.2.4-py2.5.egg/mako/runtime.py’, line 348 in _render
return context._pop_buffer().getvalue()
File ‘/Users/amaslov/Projects/dou-pylons/py/lib/python2.5/site- packages/Mako-0.2.4-py2.5.egg/mako/util.py’, line 74 in getvalue
return self.delim.join(self.data)
TypeError: sequence item 68: expected string or Unicode, NoneType found
Mako 的邮件列表曾在2009年遇到这个错误，讨论信息在[这里](http://www.mail-archive.com/pylons- discuss@googlegroups.com/msg11021.html)（需翻墙）
讨论了半天也没什么结果，一直围绕在 default_filter 上面，我改了半天，也没效果。
测试服务器和正式环境都没有问题，最后试了清空data/session, data/templates 目录，终于没错误了。
Google 上这个错误信息资料太少，我就记下来，如果哪位同学出现同样错误找到我这里，就方便解决了。
原文链接: TypeError: sequence item 22: expected string or Unicode, long found | Log4D
3a1ff193cee606bd1e2ea554a16353ee
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