­In tal, you can create your own custom namespace, which you can call directly in tal. This is a powerful, clean way to reuse code among various templates.

First, an example to give you an idea of what you can use for this:

<span tal:replace="context/modified/dateutils:long">Tuesday - Jul 15, 2008</span>

<span tal:replace="context/modified/dateutils:short">07/15/2008</span>

And you get that without having to *anything* in your template. No creating of a view method, inheriting from some base class, relying on acquisition, nothing.

This is implemented as a named adapter under the hood. In the example above, the datetime (context/modified) is the context, the name is "dateutils", and "long"/"short" are methods called on the adapter. Here's what the implementation might look like:

from zope.traversing.interfaces import IPathAdapter
from zope.tales.interfaces import ITALESFunctionNamespace
from zope import interface
from zope import component

class DateUtils(object):
    component.adapts(interface.Interface)
    interface.implements(ITALESFunctionNamespace, IPathAdapter)

    def __init__(self, context):
        if callable(context):
            self.context = context()
        else:
            self.context = context

    def long(self):
        return self.context.strftime('%A - %b %d, %Y')

    def short(self):
        return self.context.strftime('%m/%d/%y')

    def setEngine(self, engine):
­­        pass

Then we need to wire it up through zcml.