So far as I know there’s no way to make it a one-liner in current Python without introducing another function, e.g.:
split_list = lambda lst: (lst[0], lst[1:])
head, rest = split_list(my_func())
However, in Python 3.0 the specialized syntax used for variadic argument signatures and argument unpacking will become available for this type of general sequence unpacking as well, so in 3.0 you’ll be able to write:
head, *rest = my_func()
See PEP 3132 for details.