Updated April 11, 2023 for SQLAlchemy 2.0
Updated April 15, 2023 for deployment at Render.com
See:
Building a select menu in a form
Sometimes you want to populate a drop-down menu as a means of selecting one record from your database. This can be a bit puzzling to figure out in combination with using Flask-WTF and Bootstrap-Flask and Flask-SQLAlchemy all together.
This is the simplest, most basic interface I could think of — it helps a lot if you take the time to understand how an HTML <select> element works.
How to use forms in Flask — Flask: Web Forms
This repo is the exact repo that has been successfully deployed at Render.com.
Instructions: Deploy a Flask App to Render.com
Bootstrap5 error: To get Bootstrap-Flask to work properly on the cloud server, you must edit your requirements.txt file after you generate it. Delete only one line from that file:
Flask-Bootstrap4==4.0.2
This is necessary because Bootstrap-Flask will install that on its own, and having the line already in the requirements.txt file creates a conflict that will prevent your app from deploying (April 15, 2023).
Environment variable: This app connects to a MySQL database on another server, using a connection string specific to that database. Never write your connection string into the code that you post to GitHub — it includes your username and password! Store the connection string in an environment variable. Test this first on your local computer to be sure that it works. See: Set environment variable on MacOS.
Enable database connections from Render.com: On the server where the database resides, you will need to use the Remote MySQL feature to allow another server to make requests from the database. You do this by entering the IP address(es) from which the requests will come. The app is on Render.com, so you need to get the IP addresses from there.
See: Using a MySQL database with Flask.
Adding the IP addresses: See the last page of that document for instructions on how to find the IP addresses for your app at Render.com.
CHECKLIST
- ___ Set up your MySQL database on the server (e.g. Reclaim Hosting).
- ___ Edit your Python app file to connect to that remote database. Refer to Using a MySQL database with Flask.
- ___ When your Python app works 100 percent without errors, make a BACKUP COPY of the app file for safekeeping. Put it into another folder. (Why? because you don't want to upload that file to GitHub — it has your username and password in it!)
- ___ Edit the Python app file (NOT the backup) so it uses an environment variable: Set environment variable on MacOS.
- ___ Run the app — test it from your own computer until it works perfectly. You are connecting to the remote database with the file on your laptop, using the environment variable.
- ___ When it works, follow the deploy instructions: Deploy a Flask App to Render.com. Prepare the app for GitHub and push to GitHub before you go to Render.com. NOTE THE BOOTSTRAP CAUTION (Bootstrap5 error) ABOVE!
After you commit and publish to GitHub, make sure your repo looks similar to this one. You need a .gitignore file and a requirements.txt file.
You might have a static folder in your repo. I don’t have one because I used Bootstrap-Flask and I have no images, CSS, or JavaScript.
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