Marius Gedminas wrote about a useful technique for formatting paragraphs — registering a view for “*” that does the processing for you.

While developing SchoolTool we used a bit more complicated, but slightly more secure technique — adapters implementing IPathAdapter.

To get the same effect that was described in Marius blog post you do this:

import cgi

from zope.interface import implements
from zope.traversing.interfaces import ITraversable
from zope.traversing.interfaces import IPathAdapter
from zope.component import adapts


class TalFiltersPathAdapter(object):
    """Collection of filters to be used in views for text processing."""

    adapts(None)
    implements(IPathAdapter, ITraversable)

    def __init__(self, context):
        self.context = context

    def traverse(self, name, furtherPath=()):
        handler = getattr(self, name)
        return handler(furtherPath)

    def paragraphs(self, furtherPath=()):
        if self.context is None:
            return ''
        paras = filter(None, [s.strip() for s in self.context.splitlines()])
        return "".join('<p>%s</p>\n' % cgi.escape(p)
                        for p in paras)

Register it like this:

   <zope:adapter
       for="*"
       name="filter"
       provides="zope.traversing.interfaces.IPathAdapter"
       factory=".TalFiltersPathAdapter"
       />

And use it like this:

<p tal:replace="structure object/attribute/filter:paragraphs" />

The benefits of this technique – you don’t have a zope.Public view registered on all your objects, it will not “hog” ‘paragraphs’ view name (view names unless they are registered for a specific skin are a shared resource) and you can only access this functionality from TAL templates. The downside — it is slightly more complicated and more TAL specific, so if you are not using TAL templates you can’t really use this.

Zope3