関連ワード:  how to check if list is null python    how to check if list is empty python    how to see if list is empty python    how to check that list is empty python    how to check if list is not empty python    how to check if linked list is empty python    how to check if nested list is empty python    how to check if list index is empty python    how to check if list is none in python    how to check if list is not null in python