Pandas建立空的dataframe和cumsum累加函数

探索一下Pandas的累加函数cumsum，我们可以先建立一个空的dataframe，用于存放接下来的值。

import pandas as pd

columns = ['id_','name','money']
data_frame = pd.DataFrame(columns = columns) #创建一个3列的空dataframe

1. 赋值：给每一列增加数据

#建立数据
id_ = [1, 3, 2, 3, 2]
name = ['A','B','C','D','E']
money = [100, 400, 280, 170, 500]

data_frame['id_'] = id_
data_frame['name'] = name
data_frame['money'] = money  #给dataframe赋值

print(' 1. did not cumsum is: 
'+str(data_frame))

2. 直接对 'money' 列进行cumsum：

data_frame['cumsum_money'] = data_frame['money'].cumsum()
print(' 2. the cumsum money is: 
'+str(data_frame))

3. 按照 'id_' 列的分组 group by，再进行分别cumsum，如图所示：

# 先按照id分组，再对money列进行cumsum
data_2 = data_frame.groupby(['id_'])
print(data_2)

data_frame['cumsum_money_groupby'] = data_2['money'].cumsum()
print(' 3. the cumsum money after groupby is: 
'+str(data_frame))

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