Find the "Recursive Size" of a List
Python, 42 bytes



f=lambda x:x*0==[]and len(x)+sum(map(f,x))


For a non-list, output 0. For a list, output its length plus the sum of the recursive outputs for its elements.

Lists fall above numbers and below strings in the Python 2 ordering, requiring []&lt;=x&lt;''. Instead, we check x*0==[], whereas the result of 0 for a number or '' for a string.