When comparing Flask vs Revel, the Slant community recommends Flask for most people. In the question“What are the best backend web frameworks?” Flask is ranked 7th while Revel is ranked 38th. 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
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Pros
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"
Pro Comes bundled with a code reload tool
Revel comes bundled with a code reload tool which rebuilds the project on every file change. This code reload tool is also used to run, build and deploy the Revel application that you are building.
Pro Good examples easy to understand with simple emulated MVC behavior
Pro No need to find and install external libraries
Revel 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 Easy to learn for fast development
Cons
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
Con Non-idiomatic code
Con Outdated
The world has moved past its MVC obsession. It's not the way the web works anymore. The good thing about go is that it's trivial to write a server applications (literally takes minutes). relying on a bloated, archaic framework is missing the point
Con Dead
Thankfully, this abomination is no longer being developed
Con No official support for mongo
Revel does not come with any support for MongoDB, you can integrate third-party libraries but they have been reported to crash under heavy load.