Improve language of list.index in tutorial

[pulsar17]

Documentation

The first sentence of list.index (https://docs.python.org/3/tutorial/datastructures.html) reads:

Return zero-based index in the list of the first item whose value is equal to x.

A similar desription of the index method but in the context of Common Sequence Operations (https://docs.python.org/3/library/stdtypes.html#common-sequence-operations):

s.index(x[, i[, j]])	index of the first occurrence of x in s (at or after index i and before index j)	(8)

As a non-native English speaker, the latter description reads more clearly.

Suggestion

Return zero-based index of the first item whose value is equal to x in the list.

Linked PRs

• gh-107194: Improved language of list.index in tutorial #138518
• [3.14] gh-107194: Improved language of list.index in tutorial (gh-138518) #138527
• [3.13] gh-107194: Improved language of list.index in tutorial (gh-138518) #138528

[pochmann]

The table version ("index of the first occurrence of x in s") might be best, given that the "is equal to" criterion isn't even true:

x = float('nan')
a = [x]
print(a.index(x))   # prints 0
print(a[0] == x)    # prints False

Attempt This Online!

[Jamesgo1]

This looks like a simple enough change. I'll have a go at making this amendment if that's OK.

[ricsatjr]

I will try working on this issue today, adopting pochmann's suggestion.

"Return zero-based index of the first occurrence of x in the list."