How to Change a Value in a Dictionary Stored in SQLite Database with Flask Python

Learn how to update a specific value in a dictionary that is stored in an SQLite database using Flask and SQLAlchemy. This step-by-step guide will help you understand the process clearly.
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Changing a Value in a Dictionary Stored in SQLite Database with Flask Python

When working with Flask and SQLite, you may encounter situations where you need to modify data that has been previously stored in your database. One such scenario involves the modification of a specific value within a dictionary format stored in a database record. This guide will guide you through the process of effectively changing a key's value contained in a dictionary within your SQLite database using Flask and SQLAlchemy.

Understanding the Problem

In our Flask application, we have a model representing a Category that stores various products as text, which is actually a JSON encoded string. You may have populated your database with entries that look similar to this:

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

Suppose you want to change a specific variable in your stored dictionary, like replacing the value associated with the key 'b' under 'test1'. This will be illustrated with the following data structure extracted from the database:

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

When you query this data, you might have attempted to change the value like this:

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

However, this approach does not yield the desired result as the changes don't persist in the database. Let's break down what went wrong and how to fix it.

The Solution

The issue arises because the variable xLoaded is just a local instance of the data, and modifying it does not affect the original data stored in the database. You need to directly modify the x variable which holds the original SQLAlchemy object.

Step-by-Step Fix:

Fetch the Data: Retrieve your existing data from the SQLite database.

Load the JSON: Parse the JSON string to manipulate it as a Python dictionary.

Update the Value: Modify the specific value you want.

Assign It Back: Assign the updated dictionary back to the relevant field in the database object.

Commit the Changes: Use SQLAlchemy's session to commit the changes to your database.

Here’s how the corrected code should look:

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

Conclusion

Through this step-by-step guide, you should now have a clear understanding of how to modify a specific key's value within a dictionary stored in an SQLite database using Flask. Always remember to update your original database object with the modified data and commit the changes properly to ensure persistence.

This process not only applies to simple modifications like the one we've discussed but also lays the foundation for handling more complex data manipulation tasks within your Flask applications. Happy coding!