为什么元组或列表中的最后一个值索引给出不同的 class 而切片在 python 中给出不同的值？

Question

For eg if

a=(1,[2,3])

Then indexing

b=a[1]

will give class list (because index value is list)

[2, 3] <class 'list'>

but while slicing

c=a[1:]

give the class tuple

([2, 3],) <class 'tuple'>

Can anyone explain why this is so? How does Python differentiate indexing from slicing in regards to determining class?

Thank you in advance.

Answer 1

Indexing gives you a specific item within the sequence, while slicing returns a segment thereof, even if that segment is one element long.

Answer 2

A tuple consists of a number of arbitrary objects/heterogeneous items which support indexing and slicing operations.

The following will always give you a tuple:

t = tuple()

t[start:stop]
t[start:]
t[:stop]
t[:]

If you'll use indices to access objects in tuple like t[0] or t[-1] then the type will be different for different indices depending on what is present on that specific index.

Answer 3

Slicing returns a slice of a sequence (ie the same type), while indexing returns the item at that index. Compare:

>>> t = [1, 2, 3]
>>> t[1:]  # Slice -> list
[2, 3]
>>> t[1]  # Index -> int
2