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

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Answer 1

numpy uses tuples as indexes. In this case, this is a detailed slice assignment.

[0]     #means line 0 of your matrix
[(0,0)] #means cell at 0,0 of your matrix
[0:1]   #means lines 0 to 1 excluded of your matrix
[:1]    #excluding the first value means all lines until line 1 excluded
[1:]    #excluding the last param mean all lines starting form line 1 
         included
[:]     #excluding both means all lines
[::2]   #the addition of a second ':' is the sampling. (1 item every 2)
[::]    #exluding it means a sampling of 1
[:,:]   #simply uses a tuple (a single , represents an empty tuple) instead 
         of an index.

It is equivalent to the simpler

self.activity[:] = self.h

(which also works for regular lists as well)