session会话保持

#coding=utf-8
from flask import Flask
from flask import request
from flask import redirect
from flask import url_for
from flask import render_template
from flask import session


app = Flask(__name__)


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


@app.route("/user", methods=["GET", "POST"])
def check_user():
    if request.method == "POST":
        username = request.form.get("username")
        session["user"] = username
        return redirect(url_for("hello_world"))

    elif request.method == "GET":
        if "user" in session:
            return redirect(url_for("hello_world"))
        return "Please register first!"


app.secret_key = "YouWillNeverGuessWhatIThink"

if __name__ == '__main__':
    app.run(debug=True)