Dynamic Python Array Slicing

Question

I am facing a situation where I have a VERY large numpy.ndarray (really, it\'s an hdf5 dataset) that I need to find a subset of quickly because they entire arra

Answer 1

You could slice automaticaly using python's slice:

>>> a = np.random.rand(3, 4, 5)
>>> a[0, :, 0]
array([ 0.48054702,  0.88728858,  0.83225113,  0.12491976])
>>> a[(0, slice(None), 0)]
array([ 0.48054702,  0.88728858,  0.83225113,  0.12491976])

The slice method reads as slice(*start*, stop[, step]). If only one argument is passed, then it is interpreted as slice(0, stop).

In the example above : is translated to slice(0, end) which is equivalent to slice(None).

Other slice examples:

:5 -> slice(5)
1:5 -> slice(1, 5)
1: -> slice(1, None)
1::2 -> slice(1, None, 2)