numpy是否在内部存储数组的大小?

问题描述

摘自此处:

typedef struct PyArrayObject {
    PyObject_HEAD
    char *data;
    int nd;
    npy_intp *dimensions;
    npy_intp *strides;
    PyObject *base;
    PyArray_Descr *descr;
    int flags;
    PyObject *weakreflist;
} PyArrayObject;

当我查看numpy数组的规范时，我看不到它存储了数组中元素的数量.是真的吗?

When I look at the specification of a numpy array, I don't see that it stores number of elements of the array. Is that really the case?

不存储它的好处是什么?

What is the advantage of not storing that?

谢谢.

推荐答案

大小(即数组中元素的总数)计算为数组dimensions中值的乘积.该数组的长度为nd.

The size (that is, the total number of elements in the array) is computed as the product of the values in the array dimensions. The length of that array is nd.

在实现numpy核心的C代码中，您会发现宏PyArray_SIZE(obj)的许多用法.这是该宏的定义:

In the C code that implements the core of numpy, you'll find many uses of the macro PyArray_SIZE(obj). Here's the definition of that macro:

#define PyArray_SIZE(m) PyArray_MultiplyList(PyArray_DIMS(m), PyArray_NDIM(m))

不存储它的好处是，不存储冗余数据.

The advantage of not storing it is, well, not storing redundant data.

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