我已经用Python flask创建了一个登录页面，该页面连接到一个SQLite3数据库。当我输入正确的用户详细信息时，我按预期登录到系统中。但是当我输入不正确的详细信息时，登录页面只会刷新，而不会显示错误消息。

以下是我的代码

@app.route('/', methods=['GET', 'POST'])
def login():

r = ""
msg = ""
if (request.method == "POST"):
    usertype = request.form["UserType"]
    username = request.form["Username"]
    password = request.form["Password"]
    conn = sqlite3.connect("database.db")
    c = conn.cursor()
    c.execute("SELECT UserType,Username,Password FROM users WHERE UserType='" + usertype + "' and Username= '" + username + "' and Password='" + password + "'")
    r = c.fetchall()
    for i in r:
        if (usertype == i[0] and username == i[1] and password == i[2]):
            session["loginsuccess"] = True
            session["username"] = username
            return redirect(url_for("navigate"))
        else:
            msg = "Please enter correct login details"



return render_template("Login.html", msg=msg)

HTML代码

@app.route('/', methods=['GET', 'POST'])
def login():

r = ""
msg = ""
if (request.method == "POST"):
    usertype = request.form["UserType"]
    username = request.form["Username"]
    password = request.form["Password"]
    conn = sqlite3.connect("database.db")
    c = conn.cursor()
    c.execute("SELECT UserType,Username,Password FROM users WHERE UserType='" + usertype + "' and Username= '" + username + "' and Password='" + password + "'")
    r = c.fetchall()
    for i in r:
        if (usertype == i[0] and username == i[1] and password == i[2]):
            session["loginsuccess"] = True
            session["username"] = username
            return redirect(url_for("navigate"))
        else:
            msg = "Please enter correct login details"



return render_template("Login.html", msg=msg)

顺晟科技：

在您的代码库中，如果查询至少返回一个结果，则只显示您的msg，否则不会显示。所以请尝试以下代码。