The last index is exclusive: [a:b] means a <= index < b. On Jul 8, 2017 10:20 AM, <paul.carr...@free.fr> wrote:
> Hi > > Once again I need your help to understand one topic concerning slicing > topic, or in other word I do not understand how it works in that particular > (but common) case; I’m trying to reassign the 4 first values in an array: > > - If I use [:3] I’m expecting to have 4 values (index 0 to 3 included) > - Ditto with [0:3] > - If I use [3:] I have 2 values as expected (indexes 3 and 4) > > Both code and results are presented here after, so this way of thinking > worked so far in other calculations, and it fails here? > > > Thanks > > Paul > > ps : extraction from the doc (https://docs.scipy.org/doc/ > numpy/reference/arrays.indexing.html) > > *[... all indices are zero-based ...]* > > > > *Code*: > > x = np.random.rand(5); print("x = ",x); > > ## test 1 > > print("partials =\n %s \nor %s \nor %s" %( x[:3], x[0:3], x[3:]) ) > > print("x[0] : ",x[0]); print("x[1] : ",x[1]); print("x[2] : ",x[2]); > print("x[3] : ",x[3]) > > > > ## test 2 > > y = np.ones(4); print("y = ",y) > > x[0:4] = y > > print("x final = ",x) > > > *Provide*: > > x = [ 0.39921271 0.07097531 0.37044695 0.28078163 0.11590451] > > partials = > > [ 0.39921271 0.07097531 0.37044695] > > or [ 0.39921271 0.07097531 0.37044695] > > or [ 0.28078163 0.11590451] > > x[0] : 0.39921271184 > > x[1] : 0.0709753133926 > > x[2] : 0.370446946245 > > x[3] : 0.280781629 > > y = [ 1. 1. 1. 1.] > > x final = [ 1. 1. 1. 1. 0.11590451] > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@python.org > https://mail.python.org/mailman/listinfo/numpy-discussion > >
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