如何检查会话是否开启

pip install Flask Flask-Session

from flask import Flask, session
from flask_session import Session

app = Flask(__name__)
app.config["SESSION_PERMANENT"] = False
app.config["SESSION_TYPE"] = "filesystem"
Session(app)

@app.route("/")
def check_session():
    if "user_id" in session:
        return "会话已开启！"
    else:
        return "会话未开启！"

if __name__ == "__main__":
    app.run()