pandas 中groupby（）用法

https://blog.csdn.net/tanlangqie/article/details/78763285

# -*- coding: utf-8 -*-
import pandas as pd
import  numpy as np

grouped = df.groupby(['key1']).size()      #按key1的值分组，并统计个数

grouped1 = df['data1'].astype(float).groupby(df['key1']).mean()     #先将data1转换成浮点型，然后分组求均值

grouped2=df.groupby(['key1','key2']).size()      #按两列属性分组
#注意若groupby前面用df的形式则后面参数直接用['key1']的形式
print grouped2
print type(grouped2)
print '++++++++++++++++++'

grouped3=df['data1'].astype(float).groupby([df['key1'],df['add']]).mean()  #按key1与key2分组，求data1这一列均值
#注意若groupby前面用df['data1']的形式则后面参数必须用df['key1']的形式