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[英]How does NumPy multidimensional array iteration work? (With and without nditer)
[英]How does array iteration work with "and"?
如果索引有效,我想一次通过索引 +/-1 处的数组迭代三个项目。 我遇到了这个解决方案:
例子:
A = [0, 1, 2, 3, 4]
for i in range(len(A)):
print(A[i and i-1:i+2])
#[0, 1]
#[0, 1, 2]
#[1, 2, 3]
#[2, 3, 4]
#[3, 4]
A[i and i-1:i+2]
工作? 我不确定A[0 and -1:2]
如何在数组中工作。
我查看了 Python 文档并说“表达式 x 和 y 首先计算 x;如果 x 为假,则返回其值;否则,计算 y 并返回结果值。” https://docs.python.org/3/reference/expressions.html#and
但是,这似乎与数组拼接不同。
也许查看切片边界的输出会有所帮助(为了清楚起见,我在下限周围添加了括号
A = [0, 1, 2, 3, 4]
for i in range(len(A)):
print((i and i-1), i+2, A[(i and i-1):i+2])
这打印(我的评论):
0 2 [0, 1] # lower bound => (0 and -1); 0 is falsy, so 0
0 3 [0, 1, 2] # lower bound => (1 and 0); 1 is true, so 0, based on your link
1 4 [1, 2, 3] # lower bound => (2 and 1); 2 is true, so 1, based on your link
2 5 [2, 3, 4] # ...
3 6 [3, 4] # Degenerate slice indices (6) are handled gracefully
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