How to use numpy.where with logical operators

Question

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:

Answer 1

Here are two ways:

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]),)

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]),)