10 Flask Best Practices

Flask is a web application framework written in Python. It is a micro-framework that provides only the essential components of a web application. Flask is easy to get started with and has a very low learning curve.

In this article, we will discuss 10 Flask best practices that will help you write better code and improve the performance of your Flask applications.

1. Use a secret key

A secret key is used to sign cookies and other data that Flask needs to keep secure. If you don’t set a secret key, anyone will be able to modify your cookies, and they could potentially login as another user or perform other malicious actions.

To set a secret key, simply add the following line to your code:

app.secret_key = ‘your-secret-key-here’

You can generate a secret key using a tool like this one. Just make sure to keep it confidential; don’t commit it to your code repository!

2. Don’t use Flask’s development server in production

The Flask development server is not designed to be used in production. It’s meant to be used for development and testing purposes only. The main reason why you shouldn’t use it in production is because it’s not very reliable.

For example, if you’re using the development server and you get an error, the server will just crash. This can be very frustrating for users because they will be unable to access your site.

Additionally, the development server is also not very fast. If you have a lot of traffic, your site will likely be slow.

So, what should you use instead?

There are many different options available, but we recommend using a production-ready web server such as Gunicorn or uWSGI.

3. Configure logging properly

Logging is essential for understanding what’s happening in your web application. It can be used to debug errors, track user behavior, and monitor performance.

However, logging also has some security implications. If not configured properly, sensitive information such as passwords, API keys, and database queries could be written to the log file.

Therefore, it’s important to configure logging properly in Flask. The first step is to set the level of the logger to ERROR. This will ensure that only error messages are written to the log file.

Next, you should configure the format of the log message. The format should include the time, the level, the name of the logger, and the message.

Finally, you need to specify where the log file should be written. It’s best to write the log file to a location that can only be accessed by the administrator.

By following these steps, you can be sure that only relevant information is written to the log file and that sensitive information is not exposed.

4. Use Blueprints to organize your application

Blueprints help you structure your application in a logical way, and they make it easy to reuse code. For example, if you have a blueprint for an admin panel, you can easily reuse that code for another project.

Blueprints also make it easy to share code with others. If you have a blueprint that you think would be useful for someone else, you can simply share the code on GitHub or elsewhere.

Finally, blueprints make it easy to test your application. When your application is organized into blueprints, you can easily write unit tests for each blueprint. This helps ensure that your application is working as expected and helps prevent bugs.

5. Use an ORM (e.g. SQLAlchemy)

When using Flask, it’s common to see code that looks like this:

<br>@app.route('/user/<int:user_id>')<br>def user_profile(user_id):<br> user = User.query.get(user_id)<br> return render_template('user_profile.html', user=user)<br>

While there’s nothing wrong with this code, it can be improved upon by using an ORM. For example, the code above can be rewritten like this:

<br>@app.route('/user/<int:user_id>')<br>def user_profile(user_id):<br> user = db.session.query(User).get(user_id)<br> return render_template('user_profile.html', user=user)<br>

As you can see, using an ORM (in this case SQLAlchemy) can make your code more concise and easier to read.

6. Use a proper database migration tool (e.g. Alembic)

When you make changes to your database schema, such as adding a new column or table, you need a way to propagate those changes to your production environment. This is where database migration tools come in.

With Alembic, for example, you can create “migration scripts” that will automatically apply your schema changes to the production database. This way, you don’t have to manually run SQL commands or worry about making mistakes that could break your production database.

Using a database migration tool is especially important when you have multiple developers working on the same project, as it ensures that everyone is working with the same database schema.

7. Test your code

When you’re building a Flask app, there are a lot of moving parts. You have your routes, your templates, your database, and your code. If any one of these pieces breaks, it can cause your entire app to break.

Testing helps to prevent this by catching errors before they happen. By writing tests for your Flask app, you can be confident that your app will work as expected, even when you make changes.

Flask comes with a built-in testing tool called Werkzeug. This tool makes it easy to test your Flask apps. To use it, you simply need to write your tests in a file called test.py.

Werkzeug will then run your tests and report any errors. You can also use a tool like Nose or pytest to run your tests. These tools make it even easier to write and run tests.

No matter which tool you use, testing is an essential best practice for Flask development.

8. Make sure you know how to scale your app

Flask is a microframework, which means that it doesn’t come with all the bells and whistles of a full-fledged web framework. This can be both good and bad –– it’s good because it makes Flask very lightweight and easy to learn, but it’s bad because it means that you have to be careful about how you scale your app.

If you’re not careful, your app will quickly become unmanageable as it grows in complexity. Therefore, it’s important to make sure you know how to scale your app before you start building it. There are a few different ways to do this, and which one you choose will depend on your specific needs.

One way to scale your Flask app is to use a tool like Gunicorn, which is a stand-alone WSGI server for Python apps. Gunicorn is great because it’s easy to set up and use, and it has a lot of features that make it perfect for scaling Flask apps.

Another way to scale your Flask app is to use a tool like uWSGI, which is a more full-featured WSGI server. uWSGI is a bit more complex than Gunicorn, but it offers a lot of features that can be helpful when scaling Flask apps.

Finally, you can also use a tool like Apache or Nginx to reverse proxy your Flask app. This is a bit more complex than using a stand-alone WSGI server, but it offers a lot of flexibility and can be helpful if you need to scale your app to a large number of users.

9. Avoid circular imports

When you have two files that import each other, it creates a circular dependency. This can lead to errors because the interpreter doesn’t know which file to load first. In addition, it can make your code difficult to read and maintain because the imports are no longer clearly defined.

To avoid these problems, you should always structure your imports so that there is only one direction of dependencies. In other words, if file A imports file B, file B should never import file A.

If you find yourself in a situation where you need to import from a file that also imports from you, you can use the __init__.py file to break the cycle. The __init__.py file is executed when a package is imported, so you can use it to import the necessary files and avoid any circular dependencies.

10. Use Python 3

Python 3 is the latest major version of the Python programming language, and it’s not backward-compatible with earlier versions. This means that code written for Python 3 will not run correctly under Python 2.7 (or any other earlier version).

Flask is a web application framework written in Python, so it naturally follows that you should use Python 3 when developing Flask applications. Not only will this ensure that your code is compatible with Flask, but it will also make it easier to take advantage of the latest features and improvements in the Python language.