Getting an Internal 500 error with flask/python/sqlalchemy in reading/displaying data

Question

The code runs fine in flask, until I add the code to return data using sqlalchemy from the database and display it using the corresponding tag in the html section. The error in pycharm is stating that:UnboundLocalError: local variable 'unames' referenced before assignment. I'm not sure that I can reference the tags as global? Am I missing something obvious?

This is a proof of concept to show that data from mysql can be returned and displayed using flask for a small project.

this is the app.py

import os

from flask import Flask
from flask import render_template
from flask import request

from flask_sqlalchemy import SQLAlchemy

project_dir = os.path.dirname(os.path.abspath(__file__))


app = Flask(__name__)
app.config["SQLALCHEMY_DATABASE_URI"] = 'mysql://username:password@localhost:3306/database'

db = SQLAlchemy(app)

class Users(db.Model):
    uname = db.Column(db.String(80), unique=True, nullable=False, primary_key=True)

    def __repr__(self):
        return "<uname: {}>".format(self.uname)


@app.route("/", methods=["GET", "POST"])
def home():
if request.form:
users = Users(uname=request.form.get("uname"))
db.session.add(users)
db.session.commit()
unames = Users.query.all()
return render_template("home.html", unames=unames)

if __name__ == "__main__":
    app.run(debug=True)'

This is the home.html code:

<h1>UserNames:</h1>
    {% for uname in unames %}
      <p>{{Users.uname}}</p>
    {% endfor %}

Expected results should be displaying 2 usernames that are in the uname column from the Users table.

Hi please fix the indentation of your home() route, i.e, is unames = Users.query.all() indented under the if request.form: block, or not? — SuperShoot
– SuperShoot, Commented Oct 21, 2019 at 2:42

Talha Junaid · Accepted Answer · 2019-10-21 03:02:21Z

1

There is a mistake in the HTML

<p>{{Users.uname}}</p>

You are referencing to Users.uname instead it should refer to the loop variable uname.uname

<h1>UserNames:</h1>
    {% for user in unames %}
      <p>{{user.uname}}</p>
    {% endfor %}

answered Oct 21, 2019 at 3:02

Talha Junaid

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