Saullo Castro - 9 months ago 41

Python Question

I have a

`numpy`

`a = np.arange(30)`

I know that I can replace the values located at positions

`indices=[2,3,4]`

`a[indices] = 999`

But how to replace the values at the positions that are not in

`indices`

`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.