Python Flask-“检查用户名是否存在于MySQL数据库中”

Question

I am running a python Flask application which takes a username and password. I wanted to check if the username exists on the Mysql database. If it does, I wanted to return " username exists" on the web page.

below is my flask code:

from flask import Flask,render_template,request,redirect
from flask_mysqldb import MySQL
import yaml

app = Flask(__name__)

db = yaml.load(open('db.yaml'))
app.config['MYSQL_HOST'] = db['mysql_host']
app.config['MYSQL_USER'] = db['mysql_user']
app.config['MYSQL_PASSWORD'] = db['mysql_password']
app.config['MYSQL_DB'] = db['mysql_db']

mysql =MySQL(app)

@app.route('/', methods=['GET','POST'])
def index():

    if request.method == 'POST' and request.method=='GET':
        #fetch form data
        userdetails = request.form
        name = userdetails['name']
        email = userdetails['email']
        cur = mysql.connection.cursor()
        new_value= cur.execute("SELECT (name,email) FROM users where name = %s and email=%s",'name','email')
        if new_value> 0:
            return "the username exists"
        else:
            return "SUCCESS!,Successfully entered into the Database"

    return render_template('index.html')

---

when i run the flask application, my web page doesnt return anything.

Answer 1

ok so i cant comment since i dont have enough reputation however to fetch the form data the request.method needs to be POST since that is when a user clicks on a button to submit the form. As Brian Driscoll stated, request.method can not be both POST and GET simultaneously, its like saying:

if bob.age == 15 and bob.age == 50 

bob cant be both 15 AND 50 years old at the same time, in the same way request.method cant be POST AND GET at the same time. so what you want to do is

if request.method == 'POST':
        userdetails = request.form
        name = userdetails['name']
        email = userdetails['email']
        cur = mysql.connection.cursor()
        new_value= cur.execute("SELECT (name,email) FROM users where name = %s and email=%s",'name','email')
        if new_value> 0:
            return "the username exists"
        else:
            return "SUCCESS!,Successfully entered into the Database"

For more info about POST , GET and other requests you can refer to the article here