[Zope] error with tal:condition="python:x in s"

[H. Christian Gromoll]

Greetings.

I was wondering if this is a bug, or if I'm just doing something wrong.

I'm trying the following page template code:

<span tal:condition="python:'string' in s"> </span>

s is a list of strings. I'm trying to condition on membership of
'string' in the list s, but I get the following error:

exceptions.TypeError on 'in ' requires character as left operand in "",
at line 56, column 4

any help would be appreciated.

regards,
Christian Gromoll