Thank you David.
But AIUI (i.e. practically not at all) Dask is about parallel computing, which is not the same thing as deferred evaluation, though doubtless they overlap.  Again AIUI, parallel computing is mainly useful when you have multiple cores or multiple computers.
Can anyone give examples (in Python pseudo-code perhaps) showing how *deferred evaluation* would be useful for a concrete task?  (Solving an equation.  Drawing a graph.  Analysing a document.  Manufacturing a widget.  Planning a journey.  Firing a missile.  Anything!  You name it.)
Best wishes
Rob Cliffe

On 08/12/2021 22:40, David Mertz, Ph.D. wrote:
On Wed, Dec 8, 2021, 2:58 PM Rob Cliffe via Python-ideas 
On 08/12/2021 19:27, Paul Moore wrote:
> The reason deferred objects keep coming up is because they *do* have a much more compelling benefit - they help in a much broader range of cases.

Can anyone provide some realistic use cases?  I've read the whole thread and I can only recall at most one, viz. the default value is expensive to compute and may not be needed. 

https://docs.dask.org/en/stable/delayed.html

This library is widely used, extremely powerful, and expressive. Basically, a built-in capability would have every win of Dask Delayed, but decrease the impedance mismatch (which isn't terrible as-is) and avoid the need for external tooling.