(REGISTER FUNCTION)

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

        if not request.form.get("username"):
            return apology ("You must provide a username")

        elif not request.form.get("password"):
            return apology ("You must provide a password")

        elif not request.form.get("confirmed_password"):
            if request.form.get("confirmed_password") != request.form.get("password"):
                return apology ("You must provide a matching password")

        encrypted = pwd_context.encrypt("password")

        rows = db.execute("INSERT INTO users (username,password) VALUES (:username, :password)",username=request.form.get("username"), password=encrypted)
        if len(rows) == 0:
            return apology("That username is taken: Please try again")
        elif len(rows) != 0:

            rows = db.execute("INSERT INTO \"portfolio_storage\" (\"portfolio_ID\",\"user_ID\") VALUES (:portfolio_ID, :user_ID)",
                portfolio_ID=request.form.get("user_ID"),
                user_ID=request.form.get("user_ID"))


        session["user_id"] = rows[0]["id"]

        return redirect(url_for("index"))

    else:
        return render_template("register.html")






(REGISTER HTML - if it helps)

{% extends "layout.html" %}

{% block title %}
    Register
{% endblock %}

{% block main %}
    <form action="{{ url_for('register') }}" method="post">
        <fieldset>
            <div class="form-group">
                <input autocomplete="off" autofocus class="form-control" name="username" placeholder="Username" type="text"/>
            </div>
            <div class="form-group">
                <input class="form-control" name="password" placeholder="Password" type="password"/>
            </div>
            <div class="form-group">
                <input class="form-control" name="confirmed_password" placeholder="Confirm Password" type="confirmed_password"/>
            </div>
            <div class="form-group">
                <button class="btn btn-default" type="submit">Register</button>
            </div>
        </fieldset>
    </form>
{% endblock %}