#导入pandas

import pandas as pd

import numpy as np

#导入SqlAlchemy

from sqlalchemy import create_engine

if __name__ == "__main__":

    #建立数据库引擎

    engine = create_engine('mysql+pymysql://root:mysql@localhost:3306/mymac')

    #写一条sql

    sql = 'select id,name,age,gender from student'

    #建立dataframe

    df = pd.read_sql_query(sql,engine)

    # print(df)

    #按照年龄倒序    正序：ascending=True

    #翻译为sql  select * from student order by asc | desc

    # df = df.sort_values(['age','gender'],ascending=False)

    # print(df)

    #取年龄最小的学生  在尾部取值

    #翻译为sql select * from student order by age limit 1

    # df = df.sort_values(['age']).tail(1)

    # print(df)

    #求整个班的平均年龄

    avg_age= df.age.mean()

    #使用loc方法指定字段

    print(df.loc[(df['age']<avg_age ) & df['gender']==1])

    #获取指定字段

    # print(df.loc[df['gender']==1,['id','name']])

    #将dataframe写入数据表,表名，数据引擎，索引是否入库

    # df.to_sql('student_copy',engine,index=False)

    #前提要安装好 openpyxl   安装命令 pip install openpyxl

    #导入成excel文件

    # df.to_excel('student.xlsx')

    # print(Student.objects.all())