python3 使用openpyxl将mysql数据写入xlsx的操作

编程的生活愈发不容易了，工作越来越难找，说多了都是泪还是给大家贡献些代码比较实际。

python3 链接数据库需要下载名为pyMySQL的第三方库

python3 读写xlsx需要下载名为openpyxl的第三方库

在此我只贡献链接数据库和写入xlsx的代码

import pymysql.cursors
from fj.util import logger
from openpyxl import Workbook
from openpyxl.compat import range
from openpyxl.utils import get_column_letter
 
# 链接数据库的游标
connect = pymysql.Connect(
  host="localhost",
  port=3306,
  user='root',
  passwd='123456',
  db='zyDB',
  charset='utf8',
)
cursor = connect.cursor()
 
# 关闭数据库链接操作
def clos_cursor():
  return cursor.close();
 
# 读取数据库数据
def query_all():
  select_sql = "select*from fj_date where fj_id not in" 
         "( select a.fj_id from ( select * from fj_date where mj_id>0 ) a " 
         "join ( SELECT * from fj_date where jb_id>0 ) b" 
         " on a.fjzz = b.fjzz and a.fj_add=b.fj_add) and mj_id>0"
  cursor.execute(select_sql);
  return cursor.fetchall();
 
# 关闭数据库链接操作
def clos_cursor():
   cursor.close();
   connect.close()
 
def read_mysql_to_xlsx():
 
  #要创建的xlsx名称
  dest_filename = 'jb_data.xlsx'
 
  wb = Workbook()
  ws1 = wb.active
  ws1.title = "fj_date"
  # 列名
  ws1.cell(row=1,column=1,value="fj_id(数据库编号)")
  ws1.cell(row=1,column=2,value="jb_id(疾病编号)")
  ws1.cell(row=1,column=3,value="mj_id(名医编号)")
  ws1.cell(row=1,column=4,value="fj_name(方剂名称)")
  ws1.cell(row=1,column=5,value="fjcc(出处)")
  ws1.cell(row=1,column=6,value="fjdm(代码)")
  ws1.cell(row=1,column=7,value="fjzc(加减)")
  ws1.cell(row=1,column=8,value="fjgx(功效)")
  ws1.cell(row=1,column=9,value="fj_add(组成)")
  ws1.cell(row=1,column=10,value="fjjj(禁忌)")
  ws1.cell(row=1,column=11,value="fjzy(方剂治验)")
  ws1.cell(row=1,column=12,value="fjzz(主治)")
  ws1.cell(row=1,column=13,value="fjyf(用法)")
  ws1.cell(row=1,column=14,value="ylzy(药理作用)")
  ws1.cell(row=1,column=15,value="gjls(各家论述)")
  ws1.cell(row=1,column=16,value="fj(方解)")
  ws1.cell(row=1,column=17,value="ks(科室)")
  ws1.cell(row=1,column=18,value="ckzl(参考资料)")
  ws1.cell(row=1,column=19,value="lcyy(临床应用)")
  ws1.cell(row=1,column=20,value="tjbq(推荐标签)")
  ws1.cell(row=1,column=21,value="zysx(注意事项)")
  ws1.cell(row=1,column=22,value="fjzb(制备方法)")
  ws1.cell(row=1,column=23,value="fg(方歌)")
  ws1.cell(row=1,column=24,value="path(路径)")
  # 循环数据写入内容
  jb_date_list = query_all()
  for i in range(2,len(jb_date_list)+1):
    ws1.cell(row=i, column=1, value=jb_date_list[i-1][0])
    ws1.cell(row=i, column=2, value=jb_date_list[i-1][1])
    ws1.cell(row=i, column=3, value=jb_date_list[i-1][2])
    ws1.cell(row=i, column=4, value=jb_date_list[i-1][3])
    ws1.cell(row=i, column=5, value=jb_date_list[i-1][4])
    ws1.cell(row=i, column=6, value=jb_date_list[i-1][5])
    ws1.cell(row=i, column=7, value=jb_date_list[i-1][6])
    ws1.cell(row=i, column=8, value=jb_date_list[i-1][7])
    ws1.cell(row=i, column=9, value=jb_date_list[i-1][8])
    ws1.cell(row=i, column=10, value=jb_date_list[i-1][9])
    ws1.cell(row=i, column=11, value=jb_date_list[i-1][10])
    ws1.cell(row=i, column=12, value=jb_date_list[i-1][11])
    ws1.cell(row=i, column=13, value=jb_date_list[i-1][12])
    ws1.cell(row=i, column=14, value=jb_date_list[i-1][13])
    ws1.cell(row=i, column=15, value=jb_date_list[i-1][14])
    ws1.cell(row=i, column=16, value=jb_date_list[i-1][15])
    ws1.cell(row=i, column=17, value=jb_date_list[i-1][16])
    ws1.cell(row=i, column=18, value=jb_date_list[i-1][17])
    ws1.cell(row=i, column=19, value=jb_date_list[i-1][18])
    ws1.cell(row=i, column=20, value=jb_date_list[i-1][19])
    ws1.cell(row=i, column=21, value=jb_date_list[i-1][20])
    ws1.cell(row=i, column=22, value=jb_date_list[i-1][21])
    ws1.cell(row=i, column=23, value=jb_date_list[i-1][22])
    ws1.cell(row=i, column=24, value=jb_date_list[i-1][23])
 
  # 创建xlsx
  wb.save(filename=dest_filename)
 
if __name__ == '__mAIn__':
  read_mysql_to_xlsx()

补充知识：Python 关闭文件释放内存的疑惑

我用with语句打开了一个4g的文件读取内容，然后程序末尾设置一个死循环，按理说with语句不是应该自动关闭文件释放资源吗？

但是系统内存一直没有释放。应该是被文件读取到的变量content一直占用吗？把content删除就会释放内存。或者去掉死循环，程序退出资源就自动释放了

既然这样的话关闭文件貌似没啥作用呢？具体释放了什么资源？

Python一直占用着将近5G的内存：

官方文档：

If you're not using the with keyword, then you should call f.close() to close the file and immediately free up any system resources used by it. If you don't explicitly close a file, Python's garbage collector will eventually destroy the object and close the open file for you, but the file may stay open for a while. Another risk is that different Python implementations will do this clean-up at different times.

After a file object is closed, either by a with statement or by calling f.close(), attempts to use the file object will automatically fail.

代码如下：

import sys
with open(r'H:BaiduNetdiskDownload4K.mp4','rb') as f:
  print(f.closed)
  content=f.read()
print(f.closed)
print(sys.getrefcount(f))
while True:
  pass