Lazy QuerySet command to get lists of objects and an attribute of a specific object

Hi all,

I am trying to write a Django QuerySet command in my view.py file.

Simplified Context:

I have a Stage class with a Foreign Key to a Sample class. 

(Sample is a blood sample that goes through different stages, such as DNA extraction, in LIMS (laboratory information management system)).

I am trying to write a Django query / Python code to retrieve from database and send as a parameter to my template, 

a list (or if possible, iterator) of stage objects and the status of the most recently modified stage object as a tuple.

I tried this:

sample.stage1_set.latest('date_modified').status

sample.stage1_set.iterator()

where sample is a Sample instance

status is an attribute of each Stage instance. However, the only status I'm interested in is the

status that corresponds to the latest (last modified) stage. 

But latest() raises DoesNotExist error if sample does not have any stages. Without using latest() and thus not

having to write try/ catch, what is a good way to do this? Default values for the list of stages and the status are [] and None, respectively.

I'm sending the status of the last modified object because that status determines the color of <td> (a column associated with a row)

for all the stage objects. If there is a way to do this on the template side, by receiving an iterator object, and updating <td> color

within the for loop that loops over stage objects, that would be amazing.

ex. (in pseudo-code)

<td>

for stage in stages:

   {{ stage }}

    if stage is last_item_of_stages:

          update_color_of_current_td

</td>

Thank you in advance.

- ML

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