利用Python进行数据分析_Pandas_数据聚合与分组运算_数据聚合

GroupBy

按发行人汇总2021年截至目前债券实际发行规模的统计

from pandas import Series,DataFrame
import pandas as pd
import pymysql

db = pymysql.connect(host='127.0.0.1',
                    port =3306,
                    user = 'root',
                    password = 'root',
                   database = 'jydb',charset='GBK')

sql = """SELECT MainCode,BondNature,Issuer,PlanIssueSize,ActualIssueSize FROM Bond_IssueNew where IssueDateStart>='2021-01-01"""

df = pd.read_sql(sql,db)
grouped = df['ActualIssueSize'].groupby(df['Issuer'])#按Issuer进行分组，并计算ActualIssueSize的和

df1 = grouped()
df1.to_excel('2.xlsx')

执行结果：

 

 

 

 对分组进行迭代

 

from pandas import Series,DataFrame
import pandas as pd
import pymysql

db = pymysql.connect(host='127.0.0.1',
                    port =3306,
                    user = 'root',
                    password = 'root',
                   database = 'jydb',charset='GBK')

sql = """SELECT MainCode,BondNature,Issuer,PlanIssueSize,ActualIssueSize FROM Bond_IssueNew where IssueDateStart>='2021-01-01'"""

df = pd.read_sql(sql,db)
for (k1,k2),group in df.groupby(['BondNature','Issuer']):
    print(k1,k2)
    print(group)

 

执行结果：

 数据聚合

from pandas import Series,DataFrame
import pandas as pd
data = pd.read_excel('F:/Jupyter/4.xlsx')#读取excel
data['%'] = data['PlanIssueSize']/data['ActualIssueSize']#添加一列表示计划发行规模与实际发行规模的比值
data[:10]#取前10行数据

执行结果：

面向列的多函数应用

 

 

5.xlsx文件内容如下：

 

 

from pandas import Series,DataFrame
import pandas as pd
df = pd.read_excel('F:/Jupyter/5.xlsx')
grouped = df.groupby(['sex'])#根据性别分组
grouped_sex = grouped['math']
gp = grouped_sex .agg(['mean','sum','median'])#根据性别聚合mean\sum\median的值
gp

执行结果：

通过函数的方式，如下function函数的方式：

from pandas import Series,DataFrame
import pandas as pd
df = pd.read_excel('F:/Jupyter/6.xlsx')
grouped = df.groupby(['sex'])#根据性别分组
function = ['mean','sum','median']
classtype = ['chinese','math','english']
gp = grouped[classtype].agg(function)#根据性别聚合不同学科的mean\sum\median的值
gp

执行结果：

不同的列，应用不同的函数，怎么办？

向agg传入一个列名对应函数的dict（字典）

from pandas import Series,DataFrame
import pandas as pd
df = pd.read_excel('F:/Jupyter/6.xlsx')
grouped = df.groupby(['sex'])#根据性别分组
# function = ['mean','sum','median']
function_dict = {'chinese':['mean','sum'],'math':'sum','english':'median'}
classtype = ['chinese','math','english']
gp = grouped[classtype].agg(function_dict)
gp

执行结果：