(pypi)=
# 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.
(micropip-installing-from-arbitrary-urls)=
## 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 (`pip wheel`,
`setup.py bdist_wheel`).
All required dependencies need also to be previously installed with `micropip`
or `pyodide.loadPackage`.
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 {ref}`using_from_javascript`
a complete example would be,
```html
```