sum and strings

[Rhamphoryncus]

Paddy wrote:
> Rhamphoryncus wrote:
>
> >
> > It's worthwhile to note that the use of + as the concatenation operator
> > is arbitrary.  It could just have well been | or &, and has no
> > relationship with mathematically addition.
>
> The effect of the string concatenation operator is only secondary.
> Secondary to the use of the word sum; and what could be 'reasonably'
> concieved as sum's effect on  non-numeric types.
> >
> > It's also worth stressing (not in response to your post, but others)
> > that sum([[1],[2],[3]], []) is just as bad as attempting to sum
> > strings, both conceptually (it's not mathematical addition)
>
> Unfortunately, the words sum and summation are linked to other words
> that are commonly used to describe what is happening to the numders,
> the lists, and the strings.
> Words such as accumulate, concatenate, aggregate, collect, assemble, as
> well as add.

String concatenation and numeric addition only group together under the
most vague of english terms, "putting things together".  String
concatenation violates many mathematical properties of
addition/summation, and simply isn't related.

It is unfortunate that many languages (including python) promote the
confusion by using + for a "put things together" operator, ie both
mathematical addition and string concatenation.


> > I believe the prefered method to flatten a list of lists is this:
> >
> > shallow = []
> > for i in deep:
> >     shallow.extend(i)
> >
> > Yes, it's three lines.  It's also very easy to read.  reduce() and
> > sum() are not.
>
> I'd like to squeeze in the listcomp version, not because it is one line
> shorter, but because I, and maybe others prefer short listcomps such as
> the folowing:
>
> shallow = []
> [shallow.extend(i) for i in deep]

I'm sure this has been mentioned before, but listcomps are for when you
want to store the list and use it for further things, not for when you
want a side effect.  TOOWTDI.

And of course, if saving a line was the reason:

shallow = []
for i in deep: shallow.extend(i)