from flask import Flask, render_template, flash, request app = Flask(__name__) app.secret_key = "123456" @app.route("/") def hello_world(): flash("hello, mr bean") return render_template("index.html") @app.route("/login", methods=["POST"]) def login(): form = request.form username = form.get("username") password = form.get("password") if not username: flash("please input username") return render_template("index.html") if not password: flash("please input password") return render_template("index.html") if username == "mr bean" and password == "123456": flash("login success") return render_template("index.html") else: flash("username or password is wrong") return render_template("index.html") if __name__ == '__main__': app.run(debug=True) #index.html <!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>欢迎登陆</title> </head> <body> <h1>welcome</h1> <form action="/login" method="post"> <input type="text" name="username"> <input type="password" name="password"> <input type="submit" value="Submit"> </form> <h2>{{ get_flashed_messages()[0] }}</h2> </body> </html>