检查是否存在稀疏矩阵条目 [英] Check if scipy sparse matrix entry exists

问题描述

我使用

S = scipy.sparse.lil_matrix((n,n),dtype=int)

按预期，print S不显示任何内容，因为未分配任何内容. 但是如果我测试:

As expected print S doesn't show anything, since nothing has been assigned. Yet if I test:

print S[0,0]==0

我收到true.

是否可以测试以前是否设置了值?例如.按照ifempty的说法?

Is there a way to test if a value has been set before? E.g. along the lines of ifempty?

推荐答案

您可以使用

def get_items(s):
    s_coo = s.tocoo()
    return set(zip(s_coo.row, s_coo.col))

演示:

>>> n = 100
>>> s = scipy.sparse.lil_matrix((n,n),dtype=int)
>>> s[10, 12] = 1
>>> (10, 12) in get_items(s)
True

请注意，对于其他类型的稀疏矩阵，可以明确设置0:

Note that for other types of sparse matrices, 0 can be expicetely set:

>>> s = scipy.sparse.csr_matrix((n,n),dtype=int)
>>> s[12, 14] = 0
>>> (12, 14) in get_items(s)
True

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