Django and Flask are frameworks for Python, which are widely used. They have many differences, so the actual question is which of them is still better.
Generally speaking, Django should be chosen if you are writing in Python for more than three years, the site will have mostly dynamic pages in HTML, use the SQL database and want your new developers to know in advance what it’s about.
But if you have been programming for more than five years, you like reading Python code (if you compare with documents), you will have an API, you will use a service-oriented architecture (SOA) and your web applications are based on NoSQL, then definitely you need to select Flask.
Flask provides simplicity, flexibility and accuracy in work, allowing the user to choose how to implement these or other things.
Django provides an all-inclusive package: you have an admin panel, database interfaces, ORM, and a directory structure for your applications and projects.
Choose Flask, if you want more experience and learning opportunities, or if you need more control over the components used (such as databases that you need to use or interact with them).
Choose Django, if you are interested in the final product. Especially if you are working with a straightforward application, such as a news site, a store, a blog, and if you need to always have one transparent way to accomplish this or that task.
Django is a well-polished framework designed to rapidly deploy and develop a variety of Web applications written in Python. This framework has the open source code. However, there is one limitation: some things can be done in one and only one way. You can replace certain modules, but still, some internal functionality should remain unchanged. In principle, this is quite good for 95% of projects and keeps a lot of time, money and effort during development, because you have all the solutions you need right out of the box.
Flask appeared as an alternative to the Django and Pyramid frameworks because developers needed a micro-framework that allows using various components, and none of the previous frameworks allowed to modify their modules in such a large amount.
Flask is actually so simple that working in it allows an experienced programmer writing in Python to create projects in a very short time.
Django is an integral framework, perfect for startups and large companies for launching web applications. It provides all the necessary tools for operations with the application.
Flask, on the contrary, works more like a sandbox for programmers, where they can hone their skills and quickly test solutions using various modules and libraries. It is good for testing and working with less structured objects.