Is An Element of a Sequence an Object?

[Marko Rauhamaa]

Jon Forrest <nobozo at gmail.com>:

> On 6/3/2017 5:23 PM, Steve D'Aprano wrote:
>> On Sun, 4 Jun 2017 05:10 am, Jon Forrest wrote:
>
>> We can fix the book's statement by changing it to:
>>
>>      A sequence is an ordered collection of *elements* ...
>
> That's exactly what I was thinking, but then there'd have to
> be a clear definition of "element".

Instead of getting into metaphysical explanations, one should define the
concepts operationally.

A *sequence* is an object s that supports (most of) these operations:

   x in s
   x not in s
   s + t
   s * n
   n * s
   s[i]
   s[i:j]
   s[i:j:k]
   len(s)
   min(s)
   max(s)
   s.index(x[, i[, j]])
   s.count(x)

   <URL: https://docs.python.org/3/library/stdtypes.html#common-sequenc
   e-operations>

As sequence is *mutable* if it additionally supports (most of) these
operations:

   x[i] = x
   x[i:j] = t
   del s[i:j]
   s[i:j:k] = t
   del s[i:j:k]
   s.append(x)
   s.clear()
   s.copy()
   s.extend(t)
   s += t
   s *= t
   s.insert(i, x)
   s.pop([i])
   s.remove(x)
   s.reverse()

   <URL: https://docs.python.org/3/library/stdtypes.html#mutable-sequenc
   e-types>


Marko