同学笔记

• 

  weixin_46523618 2020-11-09 16:48:35

  来源：操作MySQL数据库 查看详情

  题一：如何创建MySQL数据库

  pymysql

  pip install pymysql

  from pymysql import *

  def connectDB():

      db = connect('127.0.0.1','root','1234567','meituan',charset='utf-8')

      return db

  print(type(db))

  def createTable(db):

      cursor = db.cursor()

      c = db.cursor()

      try:

      c.execute('''create table persons

                        (id int primary key not null,

                       name text not null,

                       age int not null,

                       address char(100),

                        salary real);''')

      db.commit()

      except:

          db.rollback()

          return False

  if createTable(db):

      print('create table sucess')

  else:

      print('create table failed')

  题二：如何向MySQL表中插入数据库

  def insertRecords(db):

      cursor = db.cursor()

      try:

      except Exception as e:

           print(e)

          db.rollback() 

      

          

  题三：如何查询MySQL的数据

• 

  weixin_46523618 2020-11-08 23:03:26

  来源：操作SQLite数据库 查看详情

  题一：如何创建SQLite数据库

  # create table and database

  import sqlite3

  import os

  dbPath = 'data.sqlite'

  if not os.path.exists(dbPath):

      conn = sqlite3.connect(dbPath)

      c = conn.curson()

      c.execute('''create table persons

                        (id int primary key not             null,

                       name text not null,

                       age int not null,

                       address char(100),

                        salary real);''')

      conn.commit()

      conn.close()

      print('创建数据库成功')

  题二：如何向SQLite表中插入数据

  #2.insert

  conn = sqlite3.connect(dbPath)

  c.execute('delete from persons')

  c.execute(''' insert into persons(id,name,age,address,salary)values(1,'Bill',32,'California',20000)''')

  c.execute(''' insert into persons(id,name,age,address,salary)values(2,'Mike',30,'texas',10000)''')

  c.execute(''' insert into persons(id,name,age,address,salary)values(3,'John',54,'Norway',30000)''')

  conn.commit()

  print('insert success')

  题三：如何查询SQLite表中的数据

  persons = c.execute('select name, age,address,salary from persons order by age')

  print(type(persons))

  result = []

  for person inpersons:

      value = {}

      value['name'] = person[0]

      value['age'] = person[1]

      value['name'] = person[2] 

      result.append(value)

  conn.close()

  print(type(result))

  print(result)

  import json

  resultStr = json.dumps(result)

  print(resultStr)

      

• 

  weixin_46523618 2020-11-08 23:00:28

  来源：将类的实例转换为JSON字符串 查看详情

  题一：将一个对象转化为对应的JSON字符串

  import json

  class Product:

      def __init__(self,name,price,count):

          self.name = name

          self.prince = price

          self.count = count

  product = Product('特斯拉',1000000,20)

  def product2Dict(obj):

      return {

                  'name':obj.name

                   'price':obj.price

                   'count':obj.count

                   }

  jsonStr = json.dumps(product,default=product2Dict,ensure_ascii=False)

  print(jsonStr)

  题二：将对象列表转换为JSON数组

  f = open('file/products.json','r',encoding='utf-8')

  jsonStr = f.read()

  class Product:

      def __init__(self,d):

          self.__dict__ = d

  products = json.loads(jsonStr,object_hook=Product)

  print(products)

  for product in products:

      print(product.name)

  jsonStr = json.dumps(products,default=product2Dict,ensure_ascii=False)

  print(type(jsonStr))

  总结：json模块的dumps用于将对象转换为JSON字符串，通过default参数指定一个转换函数，可以在该函数中提取对象的属性值，并生成JSON对象，最后dumps负责将转换函数返回的JSON对象转换为JSON字符串。

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