>>> # 列 A を削除
>>> del df['A']
>>> df
B C D
0 1.189704 2.138577 -0.476125
1 -1.452818 -1.147374 -2.332064
2 -1.677195 1.735829 -0.621198
3 -0.223876 0.198582 -0.126726
4 0.252367 -0.579578 0.046591
5 1.753245 0.339837 -0.432238
