register3

@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"))
           #Ensure usename don't exist already
            if  len(rows) == 0:
                #insert username and password to SQL data base
                db.execute("INSERT INTO users (username, password) VALUES(:username, :password)", username=request.form["username"], password=request.form["password"])
                #return to login.html page to login after successful register
                return render_template("login.html")
            else:
                #return apology if username already exist
                return apology("Username already exist")
        else:
            #return apology if both password don't match with each other
            return apology("both password should match")
    #Return to register.html and use post mathod
    else:
        return render_template("register.html")