[Numpy-discussion] Numpy arrays and slicing comprehension issue
paul.carrico at free.fr
paul.carrico at free.fr
Sat Jul 8 04:20:06 EDT 2017
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]
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