xlwings Lite Limitations

If any of the following limits are unacceptable, you can always switch to xlwings Server with minimal efforts to get access to a full Python installation on the backend.

Everything is Public

The most important thing to be aware of is that everything is public since the code runs on the end-user’s machine. Most importantly this includes:

  • The entire Python code

  • Configuration from the app/lite/.env file (not from the app/.env file though, which is the configuration for xlwings Server)

To see exactly what the user has access to, inspect the dist folder after running the python run.py lite command.

xlwings Limitations

Currently, the following xlwings Server features aren’t supported yet, but are likely to be added in the future:

  • App.alert()

  • Object handles

  • Streaming functions

  • Error handling: ribbon buttons and sheet button currently don’t handle errors, so use task pane buttons to call scripts.

  • Custom functions and custom scripts either have to run via xlwings Server or xlwings Lite. I.e., you can’t run some functions on the server and others locally on Wasm.

  • Only Office.js add-ins are supported. All other Integrations are not supported.

  • Static HTML pages don’t offer a way for secure authentication, so you can’t use single-sign on or any other authentication method with xlwings Lite.

PyScript/Pyodide Limitations

xlwings Lite uses PyScript, which is based on Pyodide, and comes with the following limitations:

  • The Python version, as well as the version of packages that are specifically built for Pyodide (e.g., pandas) can’t be chosen freely but are dictated by the Pyodide distribution.

  • Not all packages are supported, e.g., Polars doesn’t work. This is mainly because multithreading and multiprocessing aren’t working. Other packages may need to be built specifically for Pyodide if they aren’t available yet and if they aren’t pure Python packages, see Creating a Pyodide package. For a list of “complex” packages that are available for Pyodide, see Packages built in Pyodide

  • Imports: You can’t import Python modules via relative imports if the module is in a parent directory

  • Web APIs: you can use requests and aiohttp or pyscript.fetch(), but not httpx. Often, you’ll run into CORS issues though as the server needs to explicitly allow access via headers. GitHub works though so you can access files from there. Otherwise, you could use a CORS proxy (preferably owned by you) to work around this issue if you have no control over the web server.

  • TCP/IP connections: TCP/IP connections aren’t supported, which means that you can’t directly connect to databases like PostgreSQL. SQLite, however, is supported.

  • Since Python runs in the browser, you don’t have access to the local file system, but you could easily build a file uploader via the task pane or access them via web API.

See the Pyodide docs for further details.