__contains__ 如何为 ndarrays 工作? [英] How does __contains__ work for ndarrays?

问题描述

<预><代码>>>>x = numpy.array([[1, 2],... [3, 4],... [5, 6]])>>>[1, 7] 在 x真的>>>[1, 2] 在 x真的>>>[1, 6] 在 x真的>>>[2, 6] 在 x真的>>>[3, 6] 在 x真的>>>[2, 3] 在 x错误的>>>[2, 1] 在 x错误的>>>[1, 2, 3] 在 x错误的>>>[1, 3, 5] 在 x错误的

我不知道 __contains__ 如何用于 ndarrays.我在找的时候找不到相关的文档.它是如何工作的?它是否在任何地方都有记录?

解决方案

我在 numpy/core/src/multiarray/sequence.c.正如源代码中的评论，

x 中的东西

相当于

(x == thing).any()

对于 ndarray x，不管 x 和 thing 的维度.这仅在 thing 是标量时才有意义；当 thing 不是标量时广播的结果会导致我观察到的奇怪结果，以及像 array([1, 2, 3]) in array(1)array([1, 2, 3]) 这样的奇怪现象代码>，我没想到要尝试.确切来源是

static intarray_contains(PyArrayObject *self, PyObject *el){/* 等价于 (self == el).any() */int ret;PyObject *res, *any;res = PyArray_EnsureAnyArray(PyObject_RichCompare((PyObject *)self,el, Py_EQ));如果(res == NULL){返回-1；}any = PyArray_Any((PyArrayObject *)res, NPY_MAXDIMS, NULL);Py_DECREF(res);ret = PyObject_IsTrue(any);Py_DECREF(any);返回 ret;}

>>> x = numpy.array([[1, 2],
...                  [3, 4],
...                  [5, 6]])
>>> [1, 7] in x
True
>>> [1, 2] in x
True
>>> [1, 6] in x
True
>>> [2, 6] in x
True
>>> [3, 6] in x
True
>>> [2, 3] in x
False
>>> [2, 1] in x
False
>>> [1, 2, 3] in x
False
>>> [1, 3, 5] in x
False

I have no idea how __contains__ works for ndarrays. I couldn't find the relevant documentation when I looked for it. How does it work? And is it documented anywhere?

解决方案

I found the source for ndarray.__contains__, in numpy/core/src/multiarray/sequence.c. As a comment in the source states,

thing in x

is equivalent to

(x == thing).any()

for an ndarray x, regardless of the dimensions of x and thing. This only makes sense when thing is a scalar; the results of broadcasting when thing isn't a scalar cause the weird results I observed, as well as oddities like array([1, 2, 3]) in array(1) that I didn't think to try. The exact source is

static int
array_contains(PyArrayObject *self, PyObject *el)
{
    /* equivalent to (self == el).any() */

    int ret;
    PyObject *res, *any;

    res = PyArray_EnsureAnyArray(PyObject_RichCompare((PyObject *)self,
                                                      el, Py_EQ));
    if (res == NULL) {
        return -1;
    }
    any = PyArray_Any((PyArrayObject *)res, NPY_MAXDIMS, NULL);
    Py_DECREF(res);
    ret = PyObject_IsTrue(any);
    Py_DECREF(any);
    return ret;
}

这篇关于__contains__ 如何为 ndarrays 工作?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！