pallets/jinja

Jinja is a templating engine for Python. In plain terms, a templating engine takes a text file with placeholders and fills in real values to produce a finished document, such as an HTML web page. You write the template once, then pass different data to it as many times as needed. The syntax inside a Jinja template looks similar to Python code. You can write loops, conditionals, and labeled blocks directly in the file. One of its most useful features is template inheritance: you create a base page layout and extend it in other files, overriding only the sections that change. This keeps web projects from repeating the same header and footer code in every file. Jinja includes safety features that matter when building web applications. HTML templates can automatically escape special characters, which prevents a common security problem called XSS (cross-site scripting), where malicious input from a user could be injected into a page. There is also a sandboxed mode for safely processing templates that come from untrusted sources. Under the hood, Jinja compiles templates into Python code the first time they run and caches the result, which is why the project describes itself as fast. It also supports Python's async features, internationalization via Babel, and can be extended with custom filters and functions. Jinja is maintained by the Pallets organization, the same group that maintains the Flask web framework. It is widely used as Flask's default templating language and is one of the most common ways to generate HTML in Python web projects. The README is short and points to external documentation for fuller detail.