为什么print(arr.ravel('F'))无法执行

Question

Answer 1

不是没有生效，而是你针对的是 arr 是一维数组做 reval 散开操作，C 和 F 选项根本就没区别，你应该对一个二维数组测试区别：

这就能看到 C 和 F 的区别了
具体区别官方是这样的：

order : {‘C’,’F’, ‘A’, ‘K’}, optional
The elements of a are read using this index order. ‘C’ means to index the elements in row-major, C-style order, with the last axis index changing fastest, back to the first axis index changing slowest. ‘F’ means to index the elements in column-major, Fortran-style order, with the first index changing fastest, and the last index changing slowest. Note that the ‘C’ and ‘F’ options take no account of the memory layout of the underlying array, and only refer to the order of axis indexing. ‘A’ means to read the elements in Fortran-like index order if a is Fortran contiguous in memory, C-like order otherwise. ‘K’ means to read the elements in the order they occur in memory, except for reversing the data when strides are negative. By default, ‘C’ index order is used.

C 是按行有限展开的， F 是每一列进行展开的。