. A tag inserts a REPL block that lets you enter and run code, and a the tag works like the requirements.txt file in a repository to list needed packages.

The PyScript runtime also enables many common Python packages such as the scientific libraries that ship with Anaconda—NumPy, Pandas, Scikit-learn, and many others. Demos from the PyScript repository show different ways of doing this.

Although PyScript is still in its infancy, it already offers the ability for Python and JavaScript to interact, for Python to reference the DOM, for example, or for JavaScript objects to address Python objects. PyScript also allows in-browser equivalents for many behaviors needed in a Python distribution, such as listing package requirements for a script.

Earlier projects in this vein, like Pyodide (which PyScript uses as the basis for its own work), lacked PyScript’s seamless integration between JavaScript and Python, and its broad package access. PyScript has access to all the packages available through PyPI, with the commonly used Pandas and NumPy already available.

However, third-party packages work best if they are pure Python. PyScript does not yet have a mechanism to automatically create platform binaries for packages, although this is theoretically possible. Another hurdle is the time and bandwidth needed to download and configure all the necessary components for a given PyScript-enabled web page. The main Python runtime is about 3.4 MB of WebAssembly, although it is cached after the first load.

The goal of Anaconda for PyScript, as described in a community forum post, is to make it a possible solution to the long-standing problem of packaging and deploying Python applications. It has long been difficult to take a Python script, especially one with many dependencies, and bundle it up for someone else to use as is without the Python runtime.