input_lst = ['This', 'sentence', 'is', 'false']

def capitalize_str(string):
    return string.capitalize()

def do_stuff(lst):
    _lst = [capitalize_str(elem) for elem in lst]
    _set = {capitalize_str(elem) for elem in lst}
    _dict = {elem: capitalize_str(elem) for elem in lst}
    return _lst, _set, _dict

res = do_stuff(input_lst)

_lst = [capitalize_str(elem) for elem in input_lst]
_set = {capitalize_str(elem) for elem in input_lst}
_dict = {elem: capitalize_str(elem) for elem in input_lst}