slalchemy。将数据添加到数据库中

Question

routes.py

@app.route('/signin', methods=['GET','POST'])
def sign():
    form=forms.Signin()
    return render_template('signin',form=form)

    if request.method=='POST':

        fname=str(request.form['firstname'])
        lname=str(request.form['lastname'])
        uname=str(request.form['username'])
        btype=str(request.form['businesstype'])
        em=str(request.form['email'])
        passw=str(request.form['password'])
        repass=str(request.form['repassword'])

        sess=sessionmaker(bind=engine)
        sign=sess()

        signer=User(firstname=fname,lastname=lname,username=uname,businessType=btype,email=em,password=passw,repassword=repass)

        sign.add(signer)
        sign.commit()

        flash("Signed in. You can now log in")

        return home()

    elif request.method=='GET':
        return home()

上面的代码从登录页面中选择数据。但是，它不会使用数据更新我的数据库。我不知道哪里出错了。请帮助