Python Flatten Nested Lists

flatten_list.py

def flatten_list(l, ignore_iterables=True):
    """
    Flatten out nested lists and return a non-nested list.
    By default, ignores other iterables.
    """
    if ignore_iterables:
        arr = []
        if isinstance(l, list):
            for item in l:
                if isinstance(item, list):
                    subs = flatten_list(item,
                                        ignore_iterables=ignore_iterables)
                    for sub_item in subs:
                        arr.append(sub_item)
                else:
                    arr.append(item)
            return arr
        else:
            return [l]
    else:
        arr = []
        if hasattr(l, '__iter__'):
            for item in l:
                if hasattr(item, '__iter__'):
                    subs = flatten_list(item,
                                        ignore_iterables=ignore_iterables)
                    for sub_item in subs:
                        arr.append(sub_item)
                else:
                    arr.append(item)
            return arr
        else:
            return [l]