quickly looping over a 2D array?

[Martin]

On Jul 27, 1:46 pm, Peter Otten <__pete... at web.de> wrote:
> Martin wrote:
> > On Jul 27, 12:42 pm, Peter Otten <__pete... at web.de> wrote:
> >> Martin wrote:
> >> > I am new to python and I was wondering if there was a way to speed up
> >> > the way I index 2D arrays when I need to check two arrays
> >> > simultaneously? My current implementations is (using numpy) something
> >> > like the following...
>
> >> > for i in range(numrows):
> >> >     for j in range(numcols):
>
> >> >         if array_1[i, j] == some_value or array_2[i, j] >= array_1[i,
> >> > j] * some_other_value
> >> >             array_1[i, j] = some_new_value
>
> >> array_1[(array_1 == some_value) | (array_2 >= array_1 *
> >> some_other_value)] = some_new_value
>
> >> maybe?
>
> > So I tried...
>
> > band_1[(array_1 == 255) or (array_2 >= array_1 * factor)] = 0
>
> > which led to
>
> > ValueError: The truth value of an array with more than one element is
> > ambiguous. Use a.any() or a.all()
>
> > so not sure that works?
>
> Copy and paste -- or replace "or" with "|".

apologies - I mistook that for a type for "or"

I now get the following error...

ValueError: shape mismatch: objects cannot be broadcast to a single
shape