python如何连接mysql数据库

import pymysql

# 建立数据库连接
conn = pymysql.connect(
    host='数据库主机名',
    user='用户名',
    password='密码',
    database='数据库名'
)

# 获取游标对象
cursor = conn.cursor()

# 执行SQL语句
cursor.execute('SELECT * FROM 表名')

# 获取查询结果
result = cursor.fetchall()

# 处理查询结果
for row in result:
    print(row)

# 关闭游标和连接
cursor.close()
conn.close()

from sqlalchemy import create_engine

# 建立数据库连接
engine = create_engine('mysql+pymysql://用户名:密码@主机名:端口号/数据库名')

from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base

# 创建基类
Base = declarative_base()

# 定义数据表映射类
class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String(50))
    email = Column(String(50))

from sqlalchemy.orm import sessionmaker

# 创建会话
Session = sessionmaker(bind=engine)
session = Session()

# 查询数据
users = session.query(User).all()
for user in users:
    print(user.name, user.email)

# 关闭会话
session.close()