How can I partially fill a numpy array with a value given a range?

Question

Given a numpy array, a range, and a value, how can I fill the array with the value inside the range?

Is there a way that is faster than filling it in manually with a loop one by one?

Edit:

myArray = np.zeros(10)

What I want: [0, 0, 0, 0, 1, 1, 1, 0, 0, 0]

This is a little unclear. you can do array[range]=value if i understand you correctly. Otherwise post what you have and what you expect — Florian H
– Florian H, Commented Jun 26, 2019 at 13:34

Florian H · Accepted Answer · 2019-06-26 13:38:24Z

3

arr = np.zeros(10)
arr[4:7] = 1
print(arr)

Output:

array([0., 0., 0., 0., 1., 1., 1., 0., 0., 0.])

answered Jun 26, 2019 at 13:38

Florian H

3,0722 gold badges16 silver badges27 bronze badges

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

Comments

Claas Bontus · Accepted Answer · 2024-11-21 16:27:39Z

0

For computed ranges slices are quite useful:

ar = np.zeros(3*6).reshape((3,6))
for i in range(3):
    ar[i, slice(i+1,i+3)] = 1
print(ar)

Output:

[[0. 1. 1. 0. 0. 0.]
 [0. 0. 1. 1. 0. 0.]
 [0. 0. 0. 1. 1. 0.]]

Also, these allow specification of stride (step) values:

ar = np.zeros(2*10).reshape((2,10))
for i in range(2):
    ar[i, slice(i+1, i+8, 2)] = 2-i
print(ar)

Output:

[[0. 2. 0. 2. 0. 2. 0. 2. 0. 0.]
 [0. 0. 1. 0. 1. 0. 1. 0. 1. 0.]]

answered Nov 21, 2024 at 10:22

Claas Bontus

2,1082 gold badges20 silver badges32 bronze badges