Register.py

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

    if request.method == "POST":

        # ensure username was submitted
        if not request.form.get("username"):
            return apology("Missing username!")

        # ensure password was submitted
        elif not request.form.get("password"):
            return apology("Missing password!")

        # ensure password and confirmation match
        elif not request.form.get("password") == request.form.get("2nd_password"):
            return apology("Your password and confirmation doesn't match")

        # to store password in hash
        hashed_password = pwd_context.hash(request.form.get("password"))

        # check if username already exists
        result = db.execute("SELECT * FROM users WHERE username = :username", username=request.form.get("username"))
        if result[0]["username"] == request.form.get("username"):
            return apology("Username already exists")
        else:
            db.execute("INSERT INTO users (username, hash) VALUES(:username, :hash)", username=request.form.get("username"), hash=hashed_password)

        row = db.execute("SELECT * FROM users WHERE username = :username", username=request.form.get("username"))

        # store registered user in session
        session["user_id"] = row[0]["id"]

        # redirect user to home page
        return redirect(url_for("index"))


    # else if user reached route via GET (as by clicking a link or via redirect)
    else:
        return render_template("register.html")