Saullo Castro Saullo Castro - 1 year ago 68
Python Question

NumPy array, change the values that are NOT in a list of indices

I have a

array like:

a = np.arange(30)

I know that I can replace the values located at positions
using for instance fancy indexing:

a[indices] = 999

But how to replace the values at the positions that are not in
? Would be something like below?

a[ not in indices ] = 888

Thank you!

Answer Source

I don't know of a clean way to do something like this:

mask = np.ones(a.shape,dtype=bool) #np.ones_like(a,dtype=bool)
mask[indices] = False
a[~mask] = 999
a[mask] = 888

Of course, if you prefer to use the numpy data-type, you could use dtype=np.bool_ -- There won't be any difference in the output. it's just a matter of preference really.

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