How Anaconda’s PyScript Leverages WebAssembly to Run Python in the Browser

PyScript, developed by Anaconda, enables developers to write and execute Python directly in HTML, allowing Python code to call JavaScript libraries and build full web applications.

It is built on Pyodide, which bridges CPython to WebAssembly/Emscripten, making Python and other languages runnable in the browser via WebAssembly.

Pyodide consists of a WebAssembly‑compiled CPython 3.8 interpreter, can install any PyPI package, and provides an external function interface that exposes Python to JavaScript and the browser UI (including the DOM) to Python.

Anaconda states that strategic investment in WebAssembly (Wasm) and the open‑source Pyodide project is essential for PyScript’s success.

To further this goal, Anaconda joined the Bytecode Alliance—a consortium of Mozilla, Fastly, Intel, and Red Hat that drives WebAssembly standardization and promotes the WebAssembly System Interface (WASI) for safe access to files, network, and memory.

Wasm is crucial for PyScript, and WASI plays a key role in Python runtimes, enabling portable workloads across local, browser, and cloud environments.

Anaconda also contributes code upstream to Pyodide and supports its ongoing development, viewing Pyodide’s success as synonymous with PyScript’s success.

Beyond betting on Pyodide, Anaconda showcased a MicroPython‑based PyScript preview, which runs a tiny 303 KB runtime that loads in under 100 ms, making it ideal for constrained, OS‑less environments.

MicroPython’s small size and fast startup address performance‑critical scenarios, and because PyScript can be configured to use multiple runtimes, developers can choose the most suitable one for their use case.