python - 为什么 print、sys.stdout.write 和 os.write 不在终端中打印任何内容？

Question

在上面的代码中，当我将 print 函数放在函数和方法之外时，它可以工作，但是当我将 print、sys.stdout.write 和 os.write 函数放在函数和方法内部时，终端中不会打印任何内容？我在stackoverflow和互联网上搜索过，但没有找到原因。而且，包含打印功能的方法是在main中调用的。

# Copyright Anne M. Archibald 2008
# Released under the scipy license
from __future__ import division, print_function, absolute_import


from scipy import spatial
from sklearn.datasets.samples_generator import make_blobs,make_classification
import sys
import numpy as np
from heapq import heappush, heappop
import scipy.sparse
import os

__all__ = ['minkowski_distance_p', 'minkowski_distance',
        'Rectangle', 'KDTree']


print("I am outside functions")

def minkowski_distance_p(x, y, p=2):
    sys.stdout.write(" i am in minkowski_distance_p")
    print("i am in minkowski_distance_p")
    os.write(" i am in minkowski_distance_p")
    """
    Compute the p-th power of the L**p distance between two arrays.

    For efficiency, this function computes the L**p distance but does
    not extract the pth root. If `p` is 1 or infinity, this is equal to
    the actual L**p distance.

    Parameters
    ----------
    x : (M, K) array_like
        Input array.
    y : (N, K) array_like
        Input array.
    p : float, 1 <= p <= infinity
        Which Minkowski p-norm to use.

    Examples
    --------
    >>> minkowski_distance_p([[0,0],[0,0]], [[1,1],[0,1]])
    array([2, 1])

    """
    x = np.asarray(x)
    y = np.asarray(y)
    if p == np.inf:
        return np.amax(np.abs(y-x), axis=-1)
    elif p == 1:
        return np.sum(np.abs(y-x), axis=-1)
    else:
        return np.sum(np.abs(y-x)**p, axis=-1)


def minkowski_distance(x, y, p=2):
    """
    Compute the L**p distance between two arrays.

    Parameters
    ----------
    x : (M, K) array_like
        Input array.
    y : (N, K) array_like
        Input array.
    p : float, 1 <= p <= infinity
        Which Minkowski p-norm to use.

    Examples
    --------
    >>> minkowski_distance([[0,0],[0,0]], [[1,1],[0,1]])
    array([ 1.41421356,  1.        ])

    """
    x = np.asarray(x)
    y = np.asarray(y)
    if p == np.inf or p == 1:
        return minkowski_distance_p(x, y, p)
    else:
        return minkowski_distance_p(x, y, p)**(1./p)


class Rectangle(object):
    """Hyperrectangle class.

    Represents a Cartesian product of intervals.
    """
    def __init__(self, maxes, mins):
        """Construct a hyperrectangle."""
        self.maxes = np.maximum(maxes,mins).astype(np.float)
        self.mins = np.minimum(maxes,mins).astype(np.float)
        self.m, = self.maxes.shape

    def __repr__(self):
        return "<Rectangle %s>" % list(zip(self.mins, self.maxes))

    def volume(self):
        """Total volume."""
        return np.prod(self.maxes-self.mins)

    def split(self, d, split):
        """
        Produce two hyperrectangles by splitting.

        In general, if you need to compute maximum and minimum
        distances to the children, it can be done more efficiently
        by updating the maximum and minimum distances to the parent.

        Parameters
        ----------
        d : int
            Axis to split hyperrectangle along.
        split :
            Input.

        """
        mid = np.copy(self.maxes)
        mid[d] = split
        less = Rectangle(self.mins, mid)
        mid = np.copy(self.mins)
        mid[d] = split
        greater = Rectangle(mid, self.maxes)
        return less, greater

    def min_distance_point(self, x, p=2.):
        """
        Return the minimum distance between input and points in the hyperrectangle.

        Parameters
        ----------
        x : array_like
            Input.
        p : float, optional
            Input.

        """
        return minkowski_distance(0, np.maximum(0,np.maximum(self.mins-x,x-self.maxes)),p)

    def max_distance_point(self, x, p=2.):
        """
        Return the maximum distance between input and points in the hyperrectangle.

        Parameters
        ----------
        x : array_like
            Input array.
        p : float, optional
            Input.

        """
        return minkowski_distance(0, np.maximum(self.maxes-x,x-self.mins),p)

    def min_distance_rectangle(self, other, p=2.):
        """
        Compute the minimum distance between points in the two hyperrectangles.

        Parameters
        ----------
        other : hyperrectangle
            Input.
        p : float
            Input.

        """
        return minkowski_distance(0, np.maximum(0,np.maximum(self.mins-other.maxes,other.mins-self.maxes)),p)

    def max_distance_rectangle(self, other, p=2.):
        """
        Compute the maximum distance between points in the two hyperrectangles.

        Parameters
        ----------
        other : hyperrectangle
            Input.
        p : float, optional
            Input.

        """
        return minkowski_distance(0, np.maximum(self.maxes-other.mins,other.maxes-self.mins),p)


class KDTree(object):
    """
    kd-tree for quick nearest-neighbor lookup

    This class provides an index into a set of k-dimensional points which
    can be used to rapidly look up the nearest neighbors of any point.

    Parameters
    ----------
    data : (N,K) array_like
        The data points to be indexed. This array is not copied, and
        so modifying this data will result in bogus results.
    leafsize : int, optional
        The number of points at which the algorithm switches over to
        brute-force.  Has to be positive.

    Raises
    ------
    RuntimeError
        The maximum recursion limit can be exceeded for large data
        sets.  If this happens, either increase the value for the `leafsize`
        parameter or increase the recursion limit by::

            >>> import sys
            >>> sys.setrecursionlimit(10000)

    Notes
    -----
    The algorithm used is described in Maneewongvatana and Mount 1999.
    The general idea is that the kd-tree is a binary tree, each of whose
    nodes represents an axis-aligned hyperrectangle. Each node specifies
    an axis and splits the set of points based on whether their coordinate
    along that axis is greater than or less than a particular value.

    During construction, the axis and splitting point are chosen by the
    "sliding midpoint" rule, which ensures that the cells do not all
    become long and thin.

    The tree can be queried for the r closest neighbors of any given point
    (optionally returning only those within some maximum distance of the
    point). It can also be queried, with a substantial gain in efficiency,
    for the r approximate closest neighbors.

    For large dimensions (20 is already large) do not expect this to run
    significantly faster than brute force. High-dimensional nearest-neighbor
    queries are a substantial open problem in computer science.

    The tree also supports all-neighbors queries, both with arrays of points
    and with other kd-trees. These do use a reasonably efficient algorithm,
    but the kd-tree is not necessarily the best data structure for this
    sort of calculation.

    """
    def __init__(self, data, leafsize=10):
        print("aaa")
        self.data = np.asarray(data)
        self.n, self.m = np.shape(self.data)
        self.leafsize = int(leafsize)
        if self.leafsize < 1:
            raise ValueError("leafsize must be at least 1")
        self.maxes = np.amax(self.data,axis=0)
        self.mins = np.amin(self.data,axis=0)

        self.tree = self.__build(np.arange(self.n), self.maxes, self.mins)


    class node(object):
        if sys.version_info[0] >= 3:
            def __lt__(self, other):
                return id(self) < id(other)

            def __gt__(self, other):
                return id(self) > id(other)

            def __le__(self, other):
                return id(self) <= id(other)

            def __ge__(self, other):
                return id(self) >= id(other)

            def __eq__(self, other):
                return id(self) == id(other)

    class leafnode(node):
        def __init__(self, idx):
            self.idx = idx
            self.children = len(idx)

    class innernode(node):
        def __init__(self, split_dim, split, less, greater):
            self.split_dim = split_dim
            self.split = split
            self.less = less
            self.greater = greater
            self.children = less.children+greater.children

    def __build(self, idx, maxes, mins):
        if len(idx) <= self.leafsize:
            return KDTree.leafnode(idx)
        else:
            data = self.data[idx]
            # maxes = np.amax(data,axis=0)
            # mins = np.amin(data,axis=0)
            d = np.argmax(maxes-mins)
            maxval = maxes[d]
            minval = mins[d]
            if maxval == minval:
                # all points are identical; warn user?
                return KDTree.leafnode(idx)
            data = data[:,d]

            # sliding midpoint rule; see Maneewongvatana and Mount 1999
            # for arguments that this is a good idea.
            split = (maxval+minval)/2
            less_idx = np.nonzero(data <= split)[0]
            greater_idx = np.nonzero(data > split)[0]
            if len(less_idx) == 0:
                split = np.amin(data)
                less_idx = np.nonzero(data <= split)[0]
                greater_idx = np.nonzero(data > split)[0]
            if len(greater_idx) == 0:
                split = np.amax(data)
                less_idx = np.nonzero(data < split)[0]
                greater_idx = np.nonzero(data >= split)[0]
            if len(less_idx) == 0:
                # _still_ zero? all must have the same value
                if not np.all(data == data[0]):
                    raise ValueError("Troublesome data array: %s" % data)
                split = data[0]
                less_idx = np.arange(len(data)-1)
                greater_idx = np.array([len(data)-1])

            lessmaxes = np.copy(maxes)
            lessmaxes[d] = split
            greatermins = np.copy(mins)
            greatermins[d] = split
            return KDTree.innernode(d, split,
                    self.__build(idx[less_idx],lessmaxes,mins),
                    self.__build(idx[greater_idx],maxes,greatermins))

    def __query(self, x, k=1, eps=0, p=2, distance_upper_bound=np.inf):
        side_distances = np.maximum(0,np.maximum(x-self.maxes,self.mins-x))
        if p != np.inf:
            side_distances **= p
            min_distance = np.sum(side_distances)
        else:
            min_distance = np.amax(side_distances)

        # priority queue for chasing nodes
        # entries are:
        #  minimum distance between the cell and the target
        #  distances between the nearest side of the cell and the target
        #  the head node of the cell
        q = [(min_distance,
                tuple(side_distances),
                self.tree)]
        # priority queue for the nearest neighbors
        # furthest known neighbor first
        # entries are (-distance**p, i)
        neighbors = []

        if eps == 0:
            epsfac = 1
        elif p == np.inf:
            epsfac = 1/(1+eps)
        else:
            epsfac = 1/(1+eps)**p

        if p != np.inf and distance_upper_bound != np.inf:
            distance_upper_bound = distance_upper_bound**p

        while q:
            min_distance, side_distances, node = heappop(q)
            if isinstance(node, KDTree.leafnode):
                # brute-force
                data = self.data[node.idx]
                ds = minkowski_distance_p(data,x[np.newaxis,:],p)
                for i in range(len(ds)):
                    if ds[i] < distance_upper_bound:
                        if len(neighbors) == k:
                            heappop(neighbors)
                        heappush(neighbors, (-ds[i], node.idx[i]))
                        if len(neighbors) == k:
                            distance_upper_bound = -neighbors[0][0]
            else:
                # we don't push cells that are too far onto the queue at all,
                # but since the distance_upper_bound decreases, we might get
                # here even if the cell's too far
                if min_distance > distance_upper_bound*epsfac:
                    # since this is the nearest cell, we're done, bail out
                    break
                # compute minimum distances to the children and push them on
                if x[node.split_dim] < node.split:
                    near, far = node.less, node.greater
                else:
                    near, far = node.greater, node.less

                # near child is at the same distance as the current node
                heappush(q,(min_distance, side_distances, near))

                # far child is further by an amount depending only
                # on the split value
                sd = list(side_distances)
                if p == np.inf:
                    min_distance = max(min_distance, abs(node.split-x[node.split_dim]))
                elif p == 1:
                    sd[node.split_dim] = np.abs(node.split-x[node.split_dim])
                    min_distance = min_distance - side_distances[node.split_dim] + sd[node.split_dim]
                else:
                    sd[node.split_dim] = np.abs(node.split-x[node.split_dim])**p
                    min_distance = min_distance - side_distances[node.split_dim] + sd[node.split_dim]

                # far child might be too far, if so, don't bother pushing it
                if min_distance <= distance_upper_bound*epsfac:
                    heappush(q,(min_distance, tuple(sd), far))

        if p == np.inf:
            return sorted([(-d,i) for (d,i) in neighbors])
        else:
            return sorted([((-d)**(1./p),i) for (d,i) in neighbors])

    def query(self, x, k=1, eps=0, p=2, distance_upper_bound=np.inf):
        print("I am in the query method")
        sys.stdout.write("I am in the query method")
        os.write("I am in the query method")

        x = np.asarray(x)
        if np.shape(x)[-1] != self.m:
            raise ValueError("x must consist of vectors of length %d but has shape %s" % (self.m, np.shape(x)))
        if p < 1:
            raise ValueError("Only p-norms with 1<=p<=infinity permitted")
        retshape = np.shape(x)[:-1]
        if retshape != ():
            if k is None:
                dd = np.empty(retshape,dtype=np.object)
                ii = np.empty(retshape,dtype=np.object)
            elif k > 1:
                dd = np.empty(retshape+(k,),dtype=np.float)
                dd.fill(np.inf)
                ii = np.empty(retshape+(k,),dtype=np.int)
                ii.fill(self.n)
            elif k == 1:
                dd = np.empty(retshape,dtype=np.float)
                dd.fill(np.inf)
                ii = np.empty(retshape,dtype=np.int)
                ii.fill(self.n)
            else:
                raise ValueError("Requested %s nearest neighbors; acceptable numbers are integers greater than or equal to one, or None")
            for c in np.ndindex(retshape):
                hits = self.__query(x[c], k=k, eps=eps, p=p, distance_upper_bound=distance_upper_bound)
                if k is None:
                    dd[c] = [d for (d,i) in hits]
                    ii[c] = [i for (d,i) in hits]
                elif k > 1:
                    for j in range(len(hits)):
                        dd[c+(j,)], ii[c+(j,)] = hits[j]
                elif k == 1:
                    if len(hits) > 0:
                        dd[c], ii[c] = hits[0]
                    else:
                        dd[c] = np.inf
                        ii[c] = self.n
            return dd, ii
        else:
            hits = self.__query(x, k=k, eps=eps, p=p, distance_upper_bound=distance_upper_bound)
            if k is None:
                return [d for (d,i) in hits], [i for (d,i) in hits]
            elif k == 1:
                if len(hits) > 0:
                    return hits[0]
                else:
                    return np.inf, self.n
            elif k > 1:
                dd = np.empty(k,dtype=np.float)
                dd.fill(np.inf)
                ii = np.empty(k,dtype=np.int)
                ii.fill(self.n)
                for j in range(len(hits)):
                    dd[j], ii[j] = hits[j]
                return dd, ii
            else:
                raise ValueError("Requested %s nearest neighbors; acceptable numbers are integers greater than or equal to one, or None")








if __name__ == "__main__":
    print("I am the main")
    x, y = make_blobs(
        n_samples=10000,
        centers=4,
        n_features=2,
        center_box=(-50.0, 50.0),
        cluster_std=3,
    )
    tree = spatial.KDTree(data=x)
    pts = np.array([[0, 0], [2.1, 2.9]])
    tree.query(pts)

输出:

I am outside functions
I am the main

“查询”方法中用于打印的三个函数不打印任何内容。

Answer 1

在我看来，您从 main 中调用的 query 方法不是您定义的查询方法。您正在导入 spatial 并定义 KDTree 类，但在主代码中您正在创建 spatial.KDTree 对象。您绝对确定这是正确的对象吗？尝试删除 spatial 部分。我的建议:

if __name__ == "__main__":
    print("I am the main")
    x, y = make_blobs(
        n_samples=10000,
        centers=4,
        n_features=2,
        center_box=(-50.0, 50.0),
        cluster_std=3,
    )
    tree = KDTree(data=x)
    pts = np.array([[0, 0], [2.1, 2.9]])
    tree.query(pts)