関連ワード:  how to make an empty array in python    how to make an empty array in python numpy    how to declare an empty array in python    how to initialize an empty array in python    how to declare an empty array in python with size    how to create an empty array in python of size n    how to set an empty array in python    how to make an empty 2d array in python    how to make an empty np array in python    how to initialize an empty 2d array in python