isi() function returns a list of arrays

The problem is that isi() functions return all the individual isi vectors obtained for all the cells present in the Population. This is therefore a list of vectors with different sizes. That's why we choose to use a list of arrays instead of an array of arrays. Because each column has a different size. You can have the length of the individual elements by len(pop.isi()[idx]). But if you want to have the mean of the isi, or something else, you should rather use isi_hist() that will in fact concatenate all those isi() arrays. If that's what you want to do by the way: concatenate(pop.isi()) will return a single array with all the isi of all your cells

Cheers

I guess I gave a response to the ticket, I don't see a clever way to return a list of non homogeneous vectors. The use of concatenate(isi() ) can solve the problem