When comparing Iris vs Flask, the Slant community recommends Flask for most people. In the question“What are the best backend web frameworks?” Flask is ranked 7th while Iris is ranked 56th. The most important reason people chose Flask is:
Flask is very easy to get up and going, with vanilla HTML or with bootstrap pieces. It doesn't take much lines of Python to load Flask to get headers working, etc, and since it's all modular you don't have to have something you don't want in your application.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro No need to find and install external libraries
Iris is a "batteries included" web framework, which means that a lot of features already come out of the box. This way you don't have to spend time and find third-party libraries to integrate to the framework for most of the tasks you need to complete.
Pro Efficiency
Efficiency by using a light engine.
Pro Development
Pro API
If you're familiar with expressjs or other modern web frameworks, Iris will make you feel at home.
Pro More than feature complete
Pro More than 250 examples
More than 250 examples for implementing web application.
Pro Low amount of bugs
Most issues are questions, few bug reports and if a bug is found it's quickly patched.
Pro Good for big projects
Iris is a good framework for big projects and the author helps solving problems.
Pro Minimalist without losing power
Flask is very easy to get up and going, with vanilla HTML or with bootstrap pieces. It doesn't take much lines of Python to load Flask to get headers working, etc, and since it's all modular you don't have to have something you don't want in your application.
Pro Lots of resources available online
Flask is one of the most popular Python web frameworks, if not the most popular one. As such, there's plenty of guides, tutorials, and libraries available for it. A large number of important Python libraries, such as SQLAlchemy have libraries for Flask, which add valuable bindings to make the development process and the integration between these libraries and Flask as easy as possible.
Pro Extremely easy to build a quick prototype
Even though it's pretty minimalistic out of the box, Flask still provides the necessary tools to build a quick prototype for a web app right after a fresh install. With all the main components pretty much packed in the flask
package, building a simple web app in a single Python file is as easy as it gets.
Pro Very flexible
Flask gives developers a lot of flexibility in how they develop their web applications.
For example, the choice of not having an ORM, but instead choosing one suited to the task, or another area where Flask gives a lot of options to developers is the templating. They can use Jinja2, Flask's default templating language or choose from a number of different templating languages they desire.
Pro Great documentation
The official documentation is very thorough and complete. Everything is explained in-depth and followed by extremely well-explained tutorials that tackle real-world problems.
Pro Able to use ORM or "true SQL"
Cons
Con Previously experience with net/http
Previously experience with the Go's standard net/http package is necessary for you to move forward with Iris.
Con Author copies code
Con Not async-friendly
Flask is explicitly not designed to handle async programming.
Con Setting up a large project requires some previous knowledge of the framework
Setting up a large project with Flask is not that easy considering how there's no "official" way of doing it. Blueprints are a useful tool in this regard but require some additional reading and are a bit tricky to get right for a beginner.
The lack of some defaults can also be problematic. Having to choose between different libraries for a certain task is never easy, especially if you have never worked with Flask before.
Con Threadlocals and globals used everywhere
The default way of creating applications in flask makes it hard to use reusable and clean code.
Con HTML-oriented, not API-oriented
Not necessarily designed for making APIs, though that is possible