How to change chunks of data in a numpy array

Question

I have a large numpy 1 dimensional array of data in Python and want entries x (500) to y (520) to be changed to equal 1. I could use a for loop but is there a neater, faster numpy way of doing this?

for x in range(500,520) numpyArray[x] = 1.

Here is the for loop that could be used but it seems like there could be a function in numpy that I'm missing - I'd rather not use the masked arrays that numpy offers

Ruben Bermudez · Accepted Answer · 2014-06-17 22:22:56Z

5

You can use [] to access a range of elements:

import numpy as np

a = np.ones((10))
print(a) # Original array
# [ 1.  1.  1.  1.  1.  1.  1.  1.  1.  1.]
startindex = 2
endindex = 4
a[startindex:endindex] = 0

print(a) # modified array
# [ 1.  1.  0.  0.  1.  1.  1.  1.  1.  1.]

answered Jun 17, 2014 at 22:22

Ruben Bermudez

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