Is there a built-in way for converting a list to a function?

Suppose I have a Python list lst. I want to convert this to a function or callable, which may be done by:

def lst_as_function(idx):
    return lst[idx]

or (less preferably):

lst_as_lambda_function = lambda idx: lst[idx]

However, as this seems to be a very natural operation, I wondered whether there exists a built-in (perhaps more efficient) way to achieve this.

(To be a little bit more precise: Is there a Python built-in function convert such that I could write lst_as_function = convert(lst)?)

Does anybody know?

Answer

There actually is (if I understand your question correctly):

>>> a = [10, 20, 30, 40, 50]
>>> f = a.__getitem__
>>> f(2)
30