register2.py

@app.route("/register", methods=["GET","POST"])
def register():
    # forget any user_id
    session.clear()
    # if user reached route via POST (as by submitting a form via POST)
    if request.method == "POST":
               # ensure username was submitted
        if not request.form.get("username"):
            return apology("must provide username")

        # ensure password was submitted
        if not request.form.get("password"):
            return apology("must provide password")
        #ensure again password submitted
        if not request.form.get("again_password"):
            return apology("must provide password again")
        #ensure both password match
        if request.form.get("password") == request.form.get("again_password"):
            #query database for username
            rows = db.execute("SELECT * FROM users WHERE username = :username", username=request.form.get("username"))
            if  len(rows) != 0:
                db.execute("INSERT INTO users (username, password) VALUES(:username, :password)", username=request.form["username"], password=request.form["password"])
        else:
            print ("both password should match")
        return redirect(url_for("register"))
    else:
        return render_template("register.html")