Web Server Gateway Interface
The Web Server Gateway Interface (WSGI, pronounced whiskey or WIZ-ghee) is a specification that serves as a conduit between web servers and web applications. This interface is integral to web development in Python, providing a standardized way for Python web applications to communicate with a web server.
Background
The concept of a gateway interface is not unique to WSGI. The Common Gateway Interface (CGI) was one of the earliest specifications that allowed web servers to execute external programs to generate web content. However, CGI has several limitations, particularly in terms of performance, as it creates a new process for each request.
WSGI was introduced to address these limitations by providing a more efficient and standardized approach. Another development in the realm of gateway interfaces is the Asynchronous Server Gateway Interface (ASGI), which extends the capabilities of WSGI to support asynchronous applications.
Design and Functionality
The core idea behind WSGI is to decouple the web server from the web application, allowing each to be developed and improved independently. This is achieved by defining a common, simple calling convention. In essence, a WSGI-compliant server invokes a web application by calling it with the request details, and the application returns a response.
A typical WSGI application is a callable object that accepts two arguments: the environment, which contains request information, and a start_response callable, which starts the HTTP response. This design allows for flexibility and scalability in web applications.
Implementations and Frameworks
WSGI has become the de facto standard for Python web applications, and many modern web frameworks are built to comply with it. Some notable WSGI-compliant frameworks include:
- Flask: A micro web framework for Python known for its simplicity and flexibility.
- Django: A high-level Python web framework that encourages rapid development and clean, pragmatic design.
- Werkzeug: A WSGI utility library for Python that provides tools for building web frameworks.
WSGI is also supported by various web servers, including Apache HTTP Server and Nginx.
Comparisons with Other Interfaces
- CGI: Traditional and widely supported, but suffers from performance issues due to its process-based execution model.
- ASGI: Designed to support asynchronous applications, providing more flexibility and efficiency for handling concurrent connections.
Related Topics
The advent of WSGI has enabled the flourishing of web development in Python, providing a robust and efficient framework for building modern web applications.