原始数据： import pandas as pd import numpy as np data = {'a': [4, 6, 5, 7, 8], 'b': ['w', 't', 'y', 'x', 'z'], 'c': [1, 0, 6, -5, 3], 'd': [3, 4, 7, 10, 8], } df = pd.DataFrame(data, index=['one', 'two', 'three', 'four', '