Flatten a list of lists to a list.

list_03_flatten.py

from itertools import chain


def flatten_nested_lists(*input_list: list) -> list:
    """flatten_nested_lists.

    Args:
        input_list:

    Returns:
        list:

    >>> l1: list = []
    >>> l1.append([1, "2", 3])
    >>> l1.append([4, 5, 6, 7])
    >>> l1.append(["Eight", {"this one": 9}])
    >>> l1.append([10, 11, 12])
    >>> print(list(flatten_nested_lists(*l1)))
    [1, '2', 3, 4, 5, 6, 7, 'Eight', {'this one': 9}, 10, 11, 12]
    """
    for i in chain.from_iterable(input_list):
        yield i


l2: list = []
l2.append([1, 2, 3])
l2.append([4, 5, 6])
l2.append([10, 11, 12])

for list_item in flatten_nested_lists(*l2):
    print(list_item)