Quick Way To Access First Element In Numpy Array With Arbitrary Number Of Dimensions?

I have a function that I want to have quickly access the first (aka zeroth) element of a given Numpy array, which itself might have any number of dimensions. What's the quickest w

Solution 1:

a.flat[0]

This should be pretty fast and never require a copy. (Note that a.flat is an instance of numpy.flatiter, not an array, which is why this operation can be done without a copy.)

Solution 2:

You can use a.item(0); see the documentation at numpy.ndarray.item.

A possible disadvantage of this approach is that the return value is a Python data type, not a numpy object. For example, if a has data type numpy.uint8, a.item(0) will be a Python integer. If that is a problem, a.flat[0] is better--see @user2357112's answer.

Solution 3:

## y -- numpy array of shape (1, Ty)

if you want to get the first element:

use y.shape[0]

if you want to get the second element:

use y.shape[1]

Source: https://docs.scipy.org/doc/numpy/reference/generated/numpy.take.html

You can also use the take for more complicated extraction (to get few elements):

numpy.take(a, indices, axis=None, out=None, mode='raise')[source] Take elements from an array along an axis.