On Wed, Jul 8, 2020 at 11:18 PM Hans Ginzel <hans@matfyz.cz> wrote:

Why not to allow tuple as a list index?

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T = [[11, 12, 5, 2], [15, 6, 10], [10, 8, 12, 5], [12, 15, 8, 6]] print(T[1][2]) 10 print(T[1, 2]) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: list indices must be integers or slices, not tuple

https://stackoverflow.com/questions/40361743/python-using-tuples-as-list-ind...

Because you're not indexing a list with a two-dimensional value. You're indexing a list with a single number, which gives you another list, which you then index with another value. If you want a helper function, it's not hard to write it: def fetch(collection, indices): for index in indices: collection = collection[index] return collection Job done. This doesn't belong on the list type, because you might want the exact same behaviour starting with (or incorporating) a dict, or any other type that can be subscripted. ChrisA

On 08.07.20 15:09, Hans Ginzel wrote:

Why not to allow tuple as a list index?

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...

...

T = [[11, 12, 5, 2], [15, 6, 10], [10, 8, 12, 5], [12, 15, 8, 6]] print(T[1][2]) 10 print(T[1, 2]) Traceback (most recent call last):   File "<stdin>", line 1, in <module> TypeError: list indices must be integers or slices, not tuple

Numpy offers this convenience for multi-dimensional arrays. But in Python the sub-lists don't need to have the same length, so for example     T = [[1, 2, 3], [4], [5, 6, 7]] and then `T[1, 2]` doesn't even exist. Also it could similarly mean "get the second and third element from the list" which is what `operator.itemgetter` does:     >>> operator.itemgetter(1, 2)(T)     ([15, 6, 10], [10, 8, 12, 5])

On Wed, Jul 8, 2020 at 11:18 PM Hans Ginzel <hans@matfyz.cz> wrote:

Why not to allow tuple as a list index?

...

...

...

T = [[11, 12, 5, 2], [15, 6, 10], [10, 8, 12, 5], [12, 15, 8, 6]] print(T[1][2]) 10 print(T[1, 2]) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: list indices must be integers or slices, not tuple

https://stackoverflow.com/questions/40361743/python-using-tuples-as-list-ind...

Because you're not indexing a list with a two-dimensional value. You're indexing a list with a single number, which gives you another list, which you then index with another value. If you want a helper function, it's not hard to write it: def fetch(collection, indices): for index in indices: collection = collection[index] return collection Job done. This doesn't belong on the list type, because you might want the exact same behaviour starting with (or incorporating) a dict, or any other type that can be subscripted. ChrisA

On 08.07.20 15:09, Hans Ginzel wrote:

Why not to allow tuple as a list index?

...

...

...

T = [[11, 12, 5, 2], [15, 6, 10], [10, 8, 12, 5], [12, 15, 8, 6]] print(T[1][2]) 10 print(T[1, 2]) Traceback (most recent call last):   File "<stdin>", line 1, in <module> TypeError: list indices must be integers or slices, not tuple

Numpy offers this convenience for multi-dimensional arrays. But in Python the sub-lists don't need to have the same length, so for example     T = [[1, 2, 3], [4], [5, 6, 7]] and then `T[1, 2]` doesn't even exist. Also it could similarly mean "get the second and third element from the list" which is what `operator.itemgetter` does:     >>> operator.itemgetter(1, 2)(T)     ([15, 6, 10], [10, 8, 12, 5])