os.path.walk() to get full path of all files

[Laurent Claessens]

> file_list = []
> for root, _, filenames in os.walk(root_path):
>       for filename in filenames:
>           file_list.append(os.path.join(root, filename))


What does the notation "_" stands for ? Is it a sort of /dev/null ?

I know that in the terminal it represents the last printed text.

Laurent