Python 切片中的 `a[start:stop, i]` 是什么？

Question

Python built-in function slice 的文档是（强调我的）：

class slice(stop)
class slice(start, stop[, step])

Return a slice object representing the set of indices specified by range(start, stop, step). The start and step arguments default to None. Slice objects have read-only data attributes start, stop and step which merely return the argument values (or their default). They have no other explicit functionality; however they are used by NumPy and other third party packages. Slice objects are also generated when extended indexing syntax is used. For example: a[start:stop:step] or a[start:stop, i]. See itertools.islice() for an alternate version that returns an iterator.

a[start:stop, i] 是什么意思？

我试过了（在 Python 3.6 中）：

a = [1, 2, 3, 4, 5, 6]
a[1:3,1]

但得到了：

TypeError: list indices must be integers or slices, not tuple

Answer 1

您不能将 : 和 , 与列表结合使用。

:直接切片：

a[1:3:1]

, 与 slice 一起使用：

a[slice(1,3,1)]

然而，借助支持它的对象（如 numpy 数组），您可以在多个维度上进行切片：

import numpy as np
a = np.array([[0,1,3],[3,4,5]])
a[0:1,2]

输出：array([3])

Python 切片中的 `a[start:stop, i]` 是什么？

What is `a[start:stop, i]` in Python slicing?

python

list

built-in

slice