different methods indexing numpy arrays

Question

If I have an NxN NumPy array, and I wanted to get all rows of data from just the 5th column, is there any difference between the following methods:

just_the_fifth_a = somearray[0::,4]

just_the_fifth_b = somearray[0:,4]

just_the_fifth_c = somearray[:,4]

somearray[:-1,4] too. What are you looking for in terms of differences? — user1121588
– user1121588, Commented Jan 24, 2016 at 1:38
somearray[:-1,4] lops a value off the end. But the stop value may be the shape or larger, or may be None. — hpaulj
– hpaulj, Commented Jan 24, 2016 at 3:13
I was just looking through a tutorial and noticed that it used all of the styles I mentioned and was wondering if there was a reason for the inconsistency other than exposing reader to different styles. — Korean_Of_the_Mountain
– Korean_Of_the_Mountain, Commented Jan 24, 2016 at 22:35

Philipp Braun · Accepted Answer · 2016-01-24 01:38:58Z

1

No there is no difference between the three posted methods. You could do somearray[::,4] as well.

answered Jan 24, 2016 at 1:38

Philipp Braun

1,5732 gold badges25 silver badges41 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1