関連ワード:  how to define an empty array python    how to initialize an empty array python    how to declare an empty array python    how to define an empty matrix in python    how to declare an empty array in python with size    how to set an empty array in python    how to initialize an empty 2d array python    how to instantiate an empty array in python    how to define an empty 2d array in python    how to define an empty numpy array in python