# Installing packages from PyPI Pyodide has experimental support for installing pure Python wheels from PyPI. For use in Iodide: ``` %% py import micropip micropip.install('snowballstemmer') # Iodide implicitly waits for the promise to resolve when the packages have finished # installing... %% py import snowballstemmer stemmer = snowballstemmer.stemmer('english') stemmer.stemWords('go goes going gone'.split()) ``` For use outside of Iodide (just Python), you can use the `then` method on the `Promise` that `micropip.install` returns to do work once the packages have finished loading: ```py def do_work(*args): import snowballstemmer stemmer = snowballstemmer.stemmer('english') print(stemmer.stemWords('go goes going gone'.split())) import micropip micropip.install('snowballstemmer').then(do_work) ``` Micropip implements file integrity validation by checking the hash of the downloaded wheel against pre-recorded hash digests from the PyPi JSON API. ## Installing wheels from arbitrary URLs Pure python wheels can also be installed from any URL with micropip, ```py import micropip micropip.install( 'https://example.com/files/snowballstemmer-2.0.0-py2.py3-none-any.whl' ) ``` The wheel name in the URL must follow [PEP 427 naming convention](https://www.python.org/dev/peps/pep-0427/#file-format), which will be the case if the wheels is made using standard python tools (`wheel`, `setup.py bdist_wheel`). The remote server must set Cross-Origin Resource Sharing (CORS) headers to allow access. Otherwise, you can prepend a CORS proxy to the URL. Note however that using third-party CORS proxies has security implications, particularly since we are not able to check the file integrity, unlike with installs from PyPi. ## Complete example Adapting the setup from the section on ["using pyodide from javascript"](./using_pyodide_from_javascript.html) a complete example would be, ```html
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