keep only one tuple between 2

[paul18fr]

Hi

I've 2 tuples (coming from numpy.where) which one is necessary empty:
a = tuple1
b = tuple2

In one sentence, I'm wondering how can I keep the one that is not empty?

For example, I had a look to 'numpy.any' that give me back 'True' or 'False', but I'm not able to go further.

Thanks for your help

Paul