如何在逻辑运算符中使用numpy.where [英] How to use numpy.where with logical operators

问题描述

我正在尝试查找数组中大于a但小于b的所有元素的索引.我的语法可能只是一个问题，但这不起作用:

I'm trying to find the indices of all elements in an array that are greater than a but less than b. It's probably just a problem with my syntax but this doesn't work:

numpy.where((my_array > a) and (my_array < b))

我该如何解决?还是有更好的方法呢?

How should I fix this? Or is there a better way to do it?

谢谢！

推荐答案

以下是两种方法:

In [1]: my_array = arange(10)

In [2]: where((my_array > 3) & (my_array < 7))
Out[2]: (array([4, 5, 6]),)

In [3]: where(logical_and(my_array > 3, my_array < 7))
Out[3]: (array([4, 5, 6]),)

对于第一个(将and替换为&)，请注意适当地添加括号:&的优先级高于比较运算符.您也可以使用*，但我不建议您使用它:hacky并且不能编写可读的代码.

For the first (replacing and with &), be careful to add parentheses appropriately: & has higher precedence than the comparison operators. You can also use *, but I wouldn't recommend it: it's hacky and doesn't make for readable code.

In [4]: where((my_array > 3) * (my_array < 7))
Out[4]: (array([4, 5, 6]),)

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