8、MySql数据库连接

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import text

app = Flask(__name__)
# 主机IP地址
HOSTNAME = "127.0.0.1"
# MySql的监听端口号,默认3306
PORT = 3306
# 用户名,密码,自己设置的
USERNAME = "root"
PASSWORD = "root"
# MySql上创建的数据库名称.
DATABASE = "database_learn"

app.config['SQLALCHEMY_DATABASE_URI'] = \
    f"mysql+pymysql://{USERNAME}:{PASSWORD}@{HOSTNAME}:{PORT}/{DATABASE}?charset=utf8"


# 在app.config中设置好连接数据库信息.
# 然后使用SQLAlchemy(app)创建db对象,SQLAlchemy就会自动读取app.config中设置的连接信息.
# 读取的就是上面这个设置的地方app.config['SQLALCHEMY_DATABASE_URI']
db = SQLAlchemy(app)

# 测试连接是否成功!
# 涉及到Flask上下文的问题,所以需要加上with app.app_context().
with app.app_context():
    with db.engine.connect() as conn:
        # 注意这里需要加上text(),不然会报错
        # sqlalchemy.exc.ObjectNotExecutableError: Not an executable object: 'select 1 from dual'
        # 需要导入from sqlalchemy import text
        ret = conn.execute(text("select 1 from dual"))
        # 正常的话的应该返回(1,)
        print(ret.fetchone())


@app.route("/")
def hello_world():
    return "hello world!"


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=5001, debug=True)

效果：连接成功