Flask and React: The Era of Responsive UI


In recent years, both Javascript and Python have grown in their respective domains. While on one hand we have robust Python based web-frameworks like Django and Turbogears, Javascript has also produced some cost-efficient technologies like Angular JS. But as the market is milking these technologies day-in and day out, neither Python nor Javascript can solely meet the complex user demands. It’s well amiable integration of the two that can provide the client the solutions that they essentially need.

One such integration of the two technologies can be witnessed by bringing together the Python-based web framework – Flask and Javascript Library – React.

Simpler were those times when the Backend Technology minded its own business handling the server  and its services while the Frontend pages just had to ‘be there’ for the user to press the buttons. But alas! We live in the cruel times of Single Page Applications (SPA). These applications not only demand for stronger communication between the three application layers, but also requires every layer to be responsive to the changes made in any other two. The client-side framework in these applications, has to maintain a state ensures that any change, (User or Server triggered) in the data-model state will trigger a change in the UI.

Integration of Flask and React is one of the most effective solutions ensuring the efficiency of SPAs. Before we discuss the boons these two carry together, let’s have a look at Flask and React individually.


Written in Python, this Jinja2 template based micro framework has so far added names like Pinterest and LikedIn to its user-base. The term micro framework implies that Flask does not require any third-party libraries or tools for its operations. Thus, form validation, upload holding or data abstraction layer seem absent from this framework. But due to its support for various extensions Flask partially allows these application features to be implemented. For better efficiency of the framework, the above said extensions are frequently updated. Here are some key features of Flask that make it a popular choice for the web-application back-ends

  • Built-In standalone server for development and testing
  • Based on Jinja 2 template
  • Large character size for Unicode-Characters
  • Request Dispatching through Representational State Transfer (REST)
  • Python’s Unit Testing Framework Integrated
  • Support for client side sessions (cookies)
  • Support for Extensions for additional features
  • Compatible with the Google App Engine

React JS

Unlike Angular JS, React is just a javascript library and not a typical framework. Along with a faction of some individual developers, big names like Facebook and Instagram also maintain React JS library. 

The demand for React arrived with the increasing need of responsive page that didn’t have to be reloaded every time there was a change in data. Ability of React to React to support large data-based web-applications makes it the first choice for the front-end developers. Apart from scalability, React is also know for its processing speed and development simplicity. As told earlier, the React is responsible for the UI alone and needs to be integrated with other web-frameworks like Flask to be used in an application as a whole. Following are some key features of the javascript library:


The Javascript extension JSX is used for the components of the React library. This extension uses the tag syntax in HTML for rendering the UI components. The JSX extension is specific to React and is similar to some other PHP/XHP extensions created by Facebook.

Virtual DOM

To efficiently display the browser’s DOM and respond to the changes made by the programmer, React creates a in-memory cache. Therefore, instead of rendering the whole page, only the specific components that are actually changed, are rendered making the pages virtually more responsive.

Beyond HTML Architecture

React architecture can render more than just simple HTML tags based on the user requirements. For example, PayPal and Netflix, two of the biggies currently using React, use a feature called the isomorphic rendering. This is basically a customised feature by React that allows to render identical pages at server and client sides.

Benefits Together

As discussed earlier, Flask and React are an ideal combination for Single Page Applications where the application layers need to be highly responsive for each other. Below are some features that make the integration of these two technologies a popular pick for web-applications

Fast Processing

Due to the responsiveness of UI the end-user feels like using a desktop application instead of a website.

Division of Responsibility

Flask and React, both have equal parts to play in the web-application. Thus, none of them is solely responsible to carry out any functionality on its own. The responsibility of any logic is strategically divided between frontend and backend, making things easier for the developers.

Support for REST

RESTful APIs enable React to build the UI in its full potential. Flask’s support for Representational State Transfer at the backend makes this a heavenly combination.

Thus, integration of Flask with React JS opens up great many possibilities for web-applications. Adding some elegant features to their parent technologies Python and Javascript, these two are making the classic website development easier and more efficient.

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I am a technology freak with passion for UI technology.

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