数据库部分不能正常运行

[523120215]

作者你好，
我在抄第五章的时候，使用Flask_SQLAlchemy不能正常运行，没有找到类似的东西，烦请帮忙瞅一眼。
代码如下：

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)

# MySQL所在的主机名
HOSTNAME = "192.168.99.200"
# MySQL监听的端口号，默认3306
PORT = 3306
# 连接MySQL的用户名，读者用自己设置的
USERNAME = "root"
# 连接MySQL的密码，读者用自己的
PASSWORD = "123456"
# 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=utf8mb4"

db = SQLAlchemy(app)

with db.engine.connect() as conn:
    rs = conn.execute("select 1")
    print(rs.fetchone())

报错如下：

FLASK_APP = app.py
FLASK_ENV = development
FLASK_DEBUG = 1
In folder D:/personal/code/database
D:\personal\code\database\venv\Scripts\python.exe -m flask run --port=8000 --host=0.0.0.0
Traceback (most recent call last):
File "C:\Users\52312\AppData\Local\Programs\Python\Python38\lib\runpy.py", line 194, in _run_module_as_main
return _run_code(code, main_globals, None,
File "C:\Users\52312\AppData\Local\Programs\Python\Python38\lib\runpy.py", line 87, in run_code
exec(code, run_globals)
File "D:\personal\code\database\venv\lib\site-packages\flask_main.py", line 3, in
main()
File "D:\personal\code\database\venv\lib\site-packages\flask\cli.py", line 1047, in main
cli.main()
File "D:\personal\code\database\venv\lib\site-packages\click\core.py", line 1055, in main
rv = self.invoke(ctx)
File "D:\personal\code\database\venv\lib\site-packages\click\core.py", line 1657, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "D:\personal\code\database\venv\lib\site-packages\click\core.py", line 1404, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "D:\personal\code\database\venv\lib\site-packages\click\core.py", line 760, in invoke
return __callback(*args, **kwargs)
File "D:\personal\code\database\venv\lib\site-packages\click\decorators.py", line 84, in new_func
return ctx.invoke(f, obj, *args, **kwargs)
File "D:\personal\code\database\venv\lib\site-packages\click\core.py", line 760, in invoke
return __callback(*args, **kwargs)
File "D:\personal\code\database\venv\lib\site-packages\flask\cli.py", line 911, in run_command
raise e from None
File "D:\personal\code\database\venv\lib\site-packages\flask\cli.py", line 897, in run_command
app = info.load_app()
File "D:\personal\code\database\venv\lib\site-packages\flask\cli.py", line 308, in load_app
app = locate_app(import_name, name)
File "D:\personal\code\database\venv\lib\site-packages\flask\cli.py", line 218, in locate_app
import(module_name)
File "D:\personal\code\database\app.py", line 22, in
with db.engine.connect() as conn:
File "D:\personal\code\database\venv\lib\site-packages\flask_sqlalchemy\extension.py", line 642, in engine
return self.engines[None]
File "D:\personal\code\database\venv\lib\site-packages\flask_sqlalchemy\extension.py", line 628, in engines
app = current_app._get_current_object() # type: ignore[attr-defined]
File "D:\personal\code\database\venv\lib\site-packages\werkzeug\local.py", line 513, in _get_current_object
raise RuntimeError(unbound_message) from None
RuntimeError: Working outside of application context.

This typically means that you attempted to use functionality that needed
the current application. To solve this, set up an application context
with app.app_context(). See the documentation for more information.

进程已结束,退出代码1