python&mysql

Posted 2021-03-08 cl94

第一种方法，使用 pymysql库

import pymysql.cursors

# Connect to the database
connection = pymysql.connect(host=‘localhost‘,
                             user=‘root‘,
                             password=‘root‘,
                             db=‘spider‘,
                             charset=‘utf8mb4‘,
                             cursorclass=pymysql.cursors.DictCursor)

try:
    with connection.cursor() as cursor:
        # Create a new record
        sql = "INSERT INTO `users` (`email`, `password`) VALUES (%s, %s)"
        cursor.execute(sql, (‘[e-mail]‘, ‘very-secret‘))

    # connection is not autocommit by default. So you must commit to save
    # your changes.
    connection.commit()

    with connection.cursor() as cursor:
        # Read a single record
        sql = "SELECT `id`, `password` FROM `users` WHERE `email`=%s"
        cursor.execute(sql, (‘[e-mail]‘,))
        result = cursor.fetchone()
        print(result)
    with connection.cursor() as cursor:
        sql = "SELECT COUNT(*) as count FROM `users`"
        cursor.execute(sql)
        result = cursor.fetchone()
        print(result)
finally:
    connection.close()

此方法基于sql语句，较复杂

第二种，使用peewee库，其实peewee是基于pymysql库的一个ORM框架，将表封装成了类，将记录封装成了对象。学习成本较高

from peewee import *
from datetime import date
db = MySQLDatabase("spider",host="127.0.0.1",port=3306,user="root",password="root")
class Person(Model):
    name = CharField(max_length=20,null=True) # 最大长度20，可以为null
    birthday = DateField()
    class Meta:
        database = db
        table_name = "users"

if __name__ == "__main__":
    # 如果没表会创建表
    db.create_tables([Person])
 
# 新增数据
uncle_bob = Person(name=‘Bob‘,birthday=date(1960,1,5))
print(uncle_bob.save())
# 查询数据
# 一条(get方法在取不到数据会抛出异常)
try:
    per = Person.get(Person.name == ‘Bob‘)
except:
    print(‘娶不到‘)
else:
    print(per.name)
# 多条
# query是modelselect对象，可以当作list来操作  因为它实现了__getitem魔法方法
query = Person.select().where(Person.name == ‘Bob‘)
print(query)
for person in query:
    person.birthday = date(2020,2,2)
    # 修改数据
    person.save() #在没有数据存在的时候新增数据，存在的时候修改数据
    # 删除数据
    person.delete_instance() 
    print(‘多条：‘,person.name)