What does [:, :] mean on NumPy arrays

Question

Sorry for the stupid question. I\'m programming on PHP but found some nice code on Python and want to \"recreate\" it on PHP. But I\'m quite frustrated about the line

<

Answer 1

This is slice assignment. Technically, it calls¹

self.activity.__setitem__((slice(None,None,None),slice(None,None,None)),self.h)

which sets all of the elements in self.activity to whatever value self.h is storing. The code you have there really seems redundant. As far as I can tell, you could remove the addition on the previous line, or simply use slice assignment:

self.activity = numpy.zeros((512,512)) + self.h

or

self.activity = numpy.zeros((512,512))
self.activity[:,:] = self.h

Perhaps the fastest way to do this is to allocate an empty array and .fill it with the expected value:

self.activity = numpy.empty((512,512))
self.activity.fill(self.h)

^{1Actually, __setslice__ is attempted before calling __setitem__, but __setslice__ is deprecated, and shouldn't be used in modern code unless you have a really good reason for it.}