Using a helper browser view in Plone

configure.zcml

  <browser:page
      name="helper_view"
      for="*"
      permission="zope2.Public"
      class=".helper_view.HelperView"
      allowed_attributes="getMD5
      method2
      method3"
      />

Helper browser view.txt

Idea is to install a helper/utility browser view (it does have no template, just methods to be called).

Please note, that these files should reside in /browser of your addon (except maybe template, when it's overriden).

helper_view.py

from Products.Five.browser import BrowserView
from your.addon import md5_function

## @brief Helper view for image macros
#  @extends Products.Five.browser.BrowserView

class HelperView(BrowserView):
    """Various helper methods.
    """
    
    def getMD5(self, string):
        return md5_function(string)

template.pt

<span tal:define="helper_view context/@@helper_view">
    <tal:contents replace="python:helper_view.getMD5('my_string')">
        MD5 of the string
    </tal:contents>
</span>