checking if a list is empty

[harrismh777]

Steven D'Aprano wrote:
>> ... if not li  says nothing about what li is supposed to 'be'
> Yes, and? Neither does:
>
> isempty(li)  # li could be anything that polymorphic isempty can deal with
> li.isempty()  # li could be anything with a "isempty" method
> len(li) == 0  # li could be anything with a length (list, dict, set, ...)

      Sure.

> That's duck-typing for you, and it is generally a strength rather than a
> weakness. For those times when it is a weakness, that's where we have
> naming conventions, type-testing, and (in some languages) static types.

      I can fix almost anything with duck-type...    :)

>> >  and implies in any case that li does not exist
> It does nothing of the sort. If li doesn't exist, you get a NameError.

      That was the point.   'not' implies something that is not logical; 
which is irony extreme since 'not' is typically considered a logical 
operator.   What does it mean to say  not <list name>?  Well, apparently 
it means the list is 'empty'... but why should it mean that? Why not 
have it mean the list has been reversed in place?  Why not have it mean 
that the list isn't homogeneous?  Why not have it mean that its not 
mutable?  I could think of more... Why should 'not' mean 'empty'?

>> >  or worse is some kind of boolean.
> Only if you're still thinking in some language that isn't Python.

    Which most of us are... hate to remind you...   Python is the new 
kid on the block, and most of us are coming at this from multiple 
filters in comp sci experience.  Its just the truth.

>> >       Why not have a list method that makes this more explicit:
> For the same reason that we don't have an int method that makes zero
> testing more explicit:

> Because sometimes you can have too much explicitness.

     True.


kind regards,

m harris