__contains__如何用于ndarray? [英] How does __contains__ work for ndarrays?

问题描述

>>> 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

我不知道__contains__如何用于ndarrays.我找不到相关的文档.它是如何工作的?并且在任何地方都有记录吗?

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?

推荐答案

我在

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

thing in x

等同于

(x == thing).any()

ndarray x的

，与x和thing的尺寸无关.仅当thing是标量时才有意义； thing不是标量时的广播结果会导致我观察到怪异的结果，以及我不曾尝试尝试的array([1, 2, 3]) in array(1)之类的怪异现象.确切的来源是

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;
}

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