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Slicing arrays

NumPy Arrays : Python

Slicing arrays using a range

We can slice index using a [start:end:step] range.

  • If start is excluded, it is 0
  • If end is excluded, it is the length of the array
  • If step is excluded, it is 1

Result includes start and excludes end.

arr = np.array(["Apt", "Dynamite", "Hangin'", "Beetlebum 2012", "Song 2"])
print(arr[1:4])
# ['Dynamite' "Hangin'" 'Beetlebum 2012']
print(arr[:4])
# ['Apt' 'Dynamite' "Hangin'" 'Beetlebum 2012']
print(arr[1:])
# ['Dynamite' "Hangin'" 'Beetlebum 2012' 'Song 2']
print(arr[0:len(arr):2])
# ['Apt' "Hangin'" 'Song 2']

In case of 2-D array, specify which part and then slice.

arr = np.array([[1, 2, 3, 4, 5], [6, 7, 8, 9, 10]])

print(arr[0,2:4]) # [3 4]
print(arr[1,::2]) # [ 6 8 10]

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