Assign new value to a condition selected element of an array

user_15425920 0
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I have a problem with assigning values to a selected element of an array that I do not understand why it is happening.

I'm programming in pyhton and, although the code is much more complex, the issue I am having can be reproduced with this small code:

Yr = np.arange(0, 10)
Xg = np.arange(0, 10)

Now I want to change the value of an element that I selected as follows:

Yr[Xg>5][2] = 10

... and it does nothing:

In [275]: Yr
Out[275]: array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

Thank you.

I tried changing the type of assigned value, but it does not work either.

numpy-ndarray element arrays python
2 Answers

It's because it creates a copy of the array So you modify the copy and not the array itself

Yr[Xg>5]

is a new array

    Yr = Yr[Xg>5]
    Yr[2] = 10
    print(Yr) # will print [ 6  7 10  9]
user_185670490

As others mentioned in their answers Yr[Xg>5] is a new array and any change on it does not apply on the original array, but you can do it by using np.put like this:

np.put(Yr, np.where(Xg>5)[0][2], 10)

Or simply do this:

Yr[np.where(Xg>15)[0][2]] = 10
user_139906450
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