2020-10-31 09:02:23 +00:00
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(loading_packages)=
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2020-10-31 20:00:58 +00:00
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# Loading packages
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2019-05-03 17:43:31 +00:00
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2021-01-03 12:00:31 +00:00
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Only the Python standard library is available after importing Pyodide.
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2020-12-31 17:55:27 +00:00
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To use other packages, you’ll need to load them using either:
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2021-02-06 20:17:57 +00:00
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- {any}`pyodide.loadPackage` for packages built with pyodide, or
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2020-10-31 20:00:58 +00:00
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- `micropip.install` for pure Python packages with wheels available on PyPi or
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2020-12-31 17:55:27 +00:00
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from other URLs.
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2020-10-31 09:02:23 +00:00
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```{note}
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2020-12-31 17:55:27 +00:00
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`micropip` can also be used to load packages built in pyodide (in
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2021-02-06 20:17:57 +00:00
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which case it relies on {any}`pyodide.loadPackage`).
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2020-10-31 09:02:23 +00:00
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```
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2020-10-31 20:00:58 +00:00
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Alternatively you can run Python code without manually pre-loading packages.
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2021-02-06 20:17:57 +00:00
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You can do this with {any}`pyodide.runPythonAsync`
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2020-12-31 17:55:27 +00:00
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which will automatically download all packages that the code snippet imports.
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It only supports packages included in Pyodide (not on PyPi) at present.
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2020-10-31 09:02:23 +00:00
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## Loading packages with pyodide.loadPackage
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Packages can be loaded by name, for those included in the official pyodide
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repository using e.g.,
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2020-10-31 09:02:23 +00:00
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```js
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pyodide.loadPackage('numpy')
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```
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It is also possible to load packages from custom URLs,
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```js
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pyodide.loadPackage('https://foo/bar/numpy.js')
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```
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in which case the URL must end with `<package-name>.js`.
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When you request a package from the official repository, all of that package's
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dependencies are also loaded. Dependency resolution is not yet implemented
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when loading packages from custom URLs.
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2021-01-12 08:36:25 +00:00
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In general, loading a package twice is not permitted. However, one can override
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a dependency by loading a custom URL with the same package name before loading
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the dependent.
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2020-10-31 09:02:23 +00:00
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Multiple packages can also be loaded in a single call,
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```js
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pyodide.loadPackage(['cycler', 'pytz'])
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```
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`pyodide.loadPackage` returns a `Promise`.
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```javascript
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pyodide.loadPackage('matplotlib').then(() => {
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// matplotlib is now available
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});
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```
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(micropip)=
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## Micropip
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### Installing packages from PyPI
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2020-12-31 12:23:03 +00:00
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Pyodide supports installing pure Python wheels from PyPI with `micropip`. You
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can use the `then` method on the `Promise` that {func}`micropip.install`
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returns to do work once the packages have finished loading:
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2019-05-03 17:43:31 +00:00
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2020-05-11 08:06:33 +00:00
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```py
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2019-05-03 17:43:31 +00:00
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def do_work(*args):
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2020-05-08 21:22:33 +00:00
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import snowballstemmer
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stemmer = snowballstemmer.stemmer('english')
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print(stemmer.stemWords('go goes going gone'.split()))
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import micropip
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micropip.install('snowballstemmer').then(do_work)
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```
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2020-05-08 21:22:33 +00:00
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2020-05-11 08:30:25 +00:00
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Micropip implements file integrity validation by checking the hash of the
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downloaded wheel against pre-recorded hash digests from the PyPi JSON API.
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2020-05-11 08:06:33 +00:00
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2020-10-30 20:09:25 +00:00
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(micropip-installing-from-arbitrary-urls)=
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2020-10-31 09:02:23 +00:00
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### Installing wheels from arbitrary URLs
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2020-05-11 08:06:33 +00:00
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Pure python wheels can also be installed from any URL with micropip,
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```py
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import micropip
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micropip.install(
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'https://example.com/files/snowballstemmer-2.0.0-py2.py3-none-any.whl'
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)
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```
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2020-12-31 17:55:27 +00:00
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Micropip currently decides whether a file is a url based on whether it ends in ".whl" or not.
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2020-05-11 08:06:33 +00:00
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The wheel name in the URL must follow [PEP 427 naming
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convention](https://www.python.org/dev/peps/pep-0427/#file-format), which will
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2020-05-11 08:34:34 +00:00
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be the case if the wheels is made using standard python tools (`pip wheel`,
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`setup.py bdist_wheel`).
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2020-05-11 08:38:27 +00:00
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All required dependencies need also to be previously installed with `micropip`
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2021-02-06 20:17:57 +00:00
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or {any}`pyodide.loadPackage`.
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2020-05-11 08:38:27 +00:00
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2020-12-31 17:55:27 +00:00
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If the file is on a remote server, it must set Cross-Origin Resource Sharing (CORS) headers to
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2020-05-11 08:06:33 +00:00
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allow access. Otherwise, you can prepend a CORS proxy to the URL. Note however
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that using third-party CORS proxies has security implications, particularly
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since we are not able to check the file integrity, unlike with installs from
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PyPi.
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2020-10-31 09:02:23 +00:00
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## Example
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2020-05-08 21:22:33 +00:00
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2020-10-30 20:09:25 +00:00
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Adapting the setup from the section on {ref}`using_from_javascript`
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a complete example would be,
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2020-05-08 21:22:33 +00:00
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```html
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<html>
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<head>
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<meta charset="utf-8">
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</head>
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<body>
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2020-05-20 16:58:43 +00:00
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<script type="text/javascript">
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// set the pyodide files URL (packages.json, pyodide.asm.data etc)
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2020-12-25 21:05:54 +00:00
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window.languagePluginUrl = 'https://cdn.jsdelivr.net/pyodide/v0.16.1/full/';
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2020-05-20 16:58:43 +00:00
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</script>
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2020-12-25 21:05:54 +00:00
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<script type="text/javascript" src="https://cdn.jsdelivr.net/pyodide/v0.16.1/full/pyodide.js"></script>
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2020-05-08 21:22:33 +00:00
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<script type="text/javascript">
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pythonCode = `
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def do_work(*args):
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import snowballstemmer
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stemmer = snowballstemmer.stemmer('english')
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print(stemmer.stemWords('go goes going gone'.split()))
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import micropip
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micropip.install('snowballstemmer').then(do_work)
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`
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languagePluginLoader.then(() => {
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return pyodide.loadPackage(['micropip'])
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}).then(() => {
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pyodide.runPython(pythonCode);
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})
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</script>
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</body>
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</html>
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```
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