I wonder if the solution is to look for the earliest Python Parser of the Field Calculator question and extensively edit it to become a Community Wiki Q&A entitled Using the Python Parser of the Field Calculator of ArcGIS for Desktop? that starts something along the lines of:
This is a Community Wiki Q&A which is intended to cover any aspects of
using the Python Parser of the Field Calculator of ArcGIS for Desktop
that are not pure Python.
Pure Python questions which are beyond the beginner examples provided as
answers below should be researched/asked at Stack Overflow.
Answers could range from Removing return/newline (\n) character from Field using Python and Field Calculator?, to any of its other quirks like wrapping fields in exclamation marks (
!FieldName!), and to some of the most commonly asked "beginner Python" tips that come out of all the Q&As we have seen so far.
Candidates for the "beginner questions" to try and cover off on could come from this FAQ.
The intention would be to point all future Python Parser beginner questions back to this one as duplicates, and to redirect any complex questions related to the Field Calculator that are nevertheless pure Python to be researched/asked at Stack Overflow.
A similar approach could be used to create a Community Wiki for Using Python with the Field Calculator of QGIS.
The aim of creating these Canonical Q&As is to avoid the need for the community to answer very similar questions over and over again which adds little new value and means that visitors to the site have to wade through potentially hundreds of Q&As rather than a single very well written Q&A from the community on the topic.
Possibly relevant: What does Stack Overflow Documentation mean to GIS Stack Exchange?