下面的代码不检查现有的用户名

Question

我正在尝试注册一个用户。如果输入的用户名已经存在于数据库中，我在阻止用户注册方面有问题。

@app.route("/register", methods=["GET", "POST"])
def register():
    """Register user"""

    if request.method == "GET":
        return render_template("register.html")

    elif request.method == "POST":

        # Ensure username was submitted
        if not request.form.get("username"):
            return apology("must provide username", 400)

        # Ensure password was submitted
        elif not request.form.get("password"):
            return apology("must provide password", 400)

        # Ensure password confirmation was submitted
        elif not request.form.get("password-confirmation"):
            return apology("must provide password confirmation", 400)

        # Check if the password confirmation field matches the password field
        elif request.form.get("password-confirmation") != request.form.get("password"):
            return apology("Your passwords didn't match", 400)

        # Query database for that username
        row = db.execute("SELECT * FROM users WHERE username = ?", request.form.get("username"))

        # Database
        database = db.execute("SELECT * FROM users")

        # Ensure username is not already in the database
        if row in database:
            return apology("username already exists", 400)

        # Insert username and password into the database AND Hash user's password
        insert = db.execute("INSERT INTO users (username,hash) VALUES(?,?)" , request.form.get("username"), generate_password_hash(request.form.get("password")))

        # Remember which user has logged in
        session["user_id"] = insert

        # Redirect user to home page
        return redirect("/")

没有得到“用户名已经存在”，而是得到“内部服务器错误”.。

有人能说明一下为什么会是这样吗？

Answer 1

您的SELECT语法错了。应该是rows = db.execute("SELECT * FROM users WHERE username = :username", username=request.form.get("username"))

Answer 2

这个if row in database:永远不会是真的。

row是一个列表，所以它试图在database中找到一个列表。database本身就是一个列表，但不包含任何列表，只包含字典。

如果row不是空列表，程序将知道用户中是否已经有用户名。暗示，暗示。