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Discover the steps to take user data from HTML forms in Flask and save it into an `SQLite` database using `SQLAlchemy`.
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How to Get Data from HTML Using Flask and Save it to SQLite

If you're working with Flask, a popular web framework for Python, you might find yourself needing to collect data from users via HTML forms and store it in a database like SQLite. It's a straightforward task, but there can be a few bumps along the way—especially for beginners. In this post, we'll take a deep dive into how to properly capture user data from a form and store it in an SQLite database using SQLAlchemy. Let's explore the common pitfalls and the correct approach to ensure successful data storage.

Understanding the Problem

You may have already tried to collect form data and save it to an SQLite database but have run into some issues. It’s common to encounter errors when transitioning from a simpler method, like saving to a CSV file, to more complex database operations. The key is to understand how to handle your Flask app's request and response cycle effectively while utilizing an ORM (Object Relational Mapping) tool like SQLAlchemy.

Example Scenario

Here’s a brief overview of the steps involved when capturing user data:

Create a form in HTML.

Use Flask to handle the form submission.

Save the data to an SQLite database using SQLAlchemy.

In the example you'll see below, we will look closely at the provided code snippets that demonstrate how to collect user input and save it correctly.

Setting Up the Model

First, let’s define our SQLAlchemy model. This model will represent the data structure in the database.

[[See Video to Reveal this Text or Code Snippet]]

Points to Note:

db.Column Definitions: Each column initialized with the db.Column method will represent fields in the database table.

nullable Parameter: Indicates whether this field must have a value.

Updating the View Function

Next, we need a view function that will process the incoming form data. This is where many beginners make mistakes. Let’s see the corrected version and understand what was wrong with the initial approach.

Corrected View Function

[[See Video to Reveal this Text or Code Snippet]]

Key Improvements:

Single Instance: We instantiate a single Submission object with all the relevant data instead of creating separate instances for email, subject, and message.

Direct Submission: Use db.session.add(submission) to add the complete submission object to the session before committing.

Creating the Form

Finally, we need to make sure our form is set up correctly to call our view function. Here’s how your form should look:

[[See Video to Reveal this Text or Code Snippet]]

Important Changes:

Routing: Use {{ url_for('submit_form') }} in the action attribute. This ensures the form will submit to the correct endpoint dynamically.

Conclusion

By following these steps, you can seamlessly capture data from your HTML forms in Flask and save it into an SQLite database using SQLAlchemy. Make sure you adhere to best practices by creating a single instance of your model with all required fields populated, handling session commits correctly, and ensuring your HTML form points to the right route.

With this guide, you should be equipped to tackle form data handling in your Flask applications confidently. Happy coding!