関連ワード:  how to check not none in python    how to check not null in python    how to check variable is not none in python    how to check value is not none in python    how to check if something is not none in python    how to check if object is not none in python    how to check value is not null in python    how to check string is not null in python    how to check variable is not null in python    how to check if list is not null in python