dn writes:
Firsty, thanks for taking the time to write such a detailed reply.
> On 17/11/2020 23:35, Loris Bennett wrote:
>> dn writes:
>>
>>> On 17/11/2020 22:01, Loris Bennett wrote:
Hi,
I have a method for manipulating the membership of groups such as:
def execute(self, operation, users, group):
"""
Perform the given operation on the users with respect to the
group
"""
action = {
'get': self.get,
'add': self.add,
'delete': self.delete,
}
return action.get(operation)(users, group)
The 'get' action would return, say, a dict of users attribute, whereas
the 'add/delete' actions would return, say, nothing, and all actions
could raise an exception if something goes wrong.
The method which calls 'execute' has to print something to the terminal,
such as the attributes in the case of 'get' and 'OK' in the cases of
'add/delete' (assuming no exception occurred).
Is there a canonical way of dealing with a method which returns different
types of data, or should I just make all actions return the same data
structure so that I can generate a generic response?
>>>
>>>
>>> Is the problem caused by coding the first step before thinking of the
>>> overall
>>> task? Try diagramming or pseudo-coding the complete solution (with multiple
>>> approaches), ie the operations AND the printing and exception-handling.
>>
>> You could have a point, although I do have a reasonable idea of what the
>> task is and coming from a Perl background, Python always feels a bit
>> like pseudocode anyway (which is one of the things I like about Python).
>
> +1 the ease of Python, but can this be seductive?
>
> Per the comment about Perl/Python experience, the operative part is the
> "thinking", not the tool - as revealed in responses below...
>
> Sometimes we design one 'solution' to a problem, and forget (or 'brainwash'
> ourselves into thinking) that there might be 'another way'.
>
> It may/not apply in this case, but adjusting from a diagram-first methodology,
> to the habit of 'jumping straight into code' exhibited by many colleagues,
> before readjusting back to (hopefully) a better balance; I felt that
> coding-first often caused me to 'paint myself into a corner' with some
> 'solutions, by being too-close to the code and not 'stepping back' to take a
> wider view of the design - but enough about me...
>
>
>>> Might it be more appropriate to complete not only the get but also its
>>> reporting, as a unit. Similarly the add and whatever happens after that;
>>> and the
>>> delete, likewise.
>>
>> Currently I am already obtaining the result and doing the reporting in
>> one method, but that makes it difficult to write tests, since it
>> violates the idea that one method should, in general, just do one thing.
>> That separation would seem appropriate here, since testing whether a
>> data set is correctly retrieved from a database seems to be
>> significantly different to testing whether the
>> reporting of an action is correctly laid out and free of typos.
>
> SRP = design thinking! +1
I knew the idea, but I didn't now the TLA for it ;-)
> TDD = early testing! +1
>
> Agreed: The tasks are definitely separate. The first is data-related. The
> second
> is about presentation.
>
> In keeping with the SRP philosophy, keep the split of execution-flow into the
> three (or more) functional-tasks by data-process, but turn each of those tasks
> into two steps/routines. (once the reporting routine following "add" has been
> coded, and it comes time to implement "delete", it may become possible to
> repeat
> the pattern, and thus 're-use' the second-half...)
>
> Putting it more formally: as the second-half is effectively 'chosen' at the
> same
> time as the first, is the reporting-routine "dependent" upon the
> data-processor?
>
> function get( self, ... )
> self.get_data()
> self.present_data()
>
> function add( self, ... )
> self.add_data()
> self.report_success_fail()
>
> ...
>
> Thus, the functional task can be tested independently of any reporting
> follow-up
> (for example in "get"); whilst maintaining/multiplying SRP...
The above approach appeals to me a lot. Slight downsides are that
such 'metafunctions' by necessity non-SRP functions and that, as there
would be no point writing tests for such functions, some tools which try
to determine test coverage might moan.
>>> Otherwise the code must first decide which action-handler, and later,
>>> which result-handler - but aren't they effectively the same decision?
>>> Thus, is the reporting integral to the get (even if they are in
>>> separate routines)?
>>
>> I think you are right here. Perhaps I should just ditch the dispatch
>> table. Maybe that only
