例2.40DataFrame数据的拆分，合并和分组计算示例
import pandas as pd
import numpy as np
d = pd.DataFrame(np.random.randint(1,6,(10,4)),columns = list("ABCD"))
d1 = d[:4]
d2 = d[4:]
dd= pd.concat([d1,d2])
s1 = d.groupby('A').mean()
s2 = d.groupby('A').apply(sum)
print("学号：3008")结果如下图
