pandas分割、应用和组合(groupby)

import numpy as np
import pandas as pd

groupby对象

df1 = pd.DataFrame({
   'key':['A','B','C','A','B','C'],'data':range(6)},columns=['key','data'])
df1.groupby('key').sum()
# 将所有的列都进行求和，所以生成的是DataFrame

按列取值

df1.groupby('key')['data'].sum()

df1.groupby('key')['data'].describe()
# 可以直接调用方法

groupby对象可以按组迭代

for (m,g) in df1.groupby('key'