Re: Python Iterable

[Darshit Shah]

On Wed, Mar 27, 2024, at 17:52, Bruno Haible wrote:
> Collin Funk wrote:
>> I have also made a conscious choice not to use more abstract
>> collections like 'Iterable' even though they are recommended [4].
>> 
>> The first is because some functions check the type:
>> 
>>     def setModules(self, modules: list[str] | tuple[str]) -> None:
>>         '''Set the modules list.'''
>>         if type(modules) is list or type(modules) is tuple:
>>            # do something, or raise a TypeError
>> 
>> It is temping to use Iterable here:
>> 
>>     print(iter(list()))
>>     <list_iterator object at 0x7f7c13f5b1c0>
>>     print(iter(tuple()))
>>     <tuple_iterator object at 0x7f7c13f5b1c0>
>> 
>> but a what about a set?
>> 
>>     print(iter(set()))
>>     <set_iterator object at 0x7f7c13f56b80>
>> 
>> We would think it is okay to pass a set, but it would fail at runtime.
>> Using the uglier Union would let us know by looking or a warning if
>> using a lsp program.
>> 
>> The second reason is sorting. Since it is easy to mess up the sorting
>> for the test cases against gnulib-tool.sh, it is probably best to only
>> pass lists for now. We can change functions to Iterable or something
>> similar once we are sure it will not affect the output.
>
> I agree. My main considerations are:
>
>   - Can someone with little exposure to Python understand and modify the
>     code? When you write 'list' and the developer knows that 'list' means
>     what is known as "array" in other programming languages, they can work
>     with the code. Using the abstract interfaces that Python has does not
>     help in this aspect.

Hi Bruno,

I would argue against this line of thinking. Sure, keep it simple, but don't 
reduce the subset of Python available only to something that is easily known 
to, for e.g. a C developer. I made the same decision when writing the testsuite 
for Wget almost 10 years ago, and in hindsight I regret it. 

The thing is, when you restrict it something that can be understood by someone 
with little exposure to Python, you end up with a codebase that is alien to 
both groups, the ones that know Python and the ones that don't. You get a 
codebase that neither enjoy working with and want to maintain. 

Instead, I would argue that following the standard Python best practices is a 
better choice. The person maintaining the script needs to be a Python  
developer anyways. Might as well make it easy for them

>
>   - In some cases, it is useful to access the data structure with indices.
>     Then an 'Iterable' will not suffice, a 'list' or 'tuple' is needed.
>     What would be the point of declaring "this function needs to traverse
>     the given data only from the beginning to the end, never in the opposite
>     direction, never with random indices"? There is no advantage. It is
>     useless information. So, why bother?
>
> Bruno