For now, only one `pyodide` can be loaded in a given global scope because we need to use a global variable for package loading. This changes `loadPyodide` so that it no longer defines `globalThis.pyodide` in favor of just returning `pyodide` from `loadPyodide`. `Module` is placed on the global object as `globalThis.__pyodide_module` for the purposes of package loading. I added documentation to explicitly state that `loadPyodide` can only be run once in each global Javascript context, an error will be thrown otherwise.

This has two advantages: 
1. The returned `pyodide` module is understandable to Typescript and other code analysis, whereas the global variable is not understandable.
2. If in the future we are able to remove the global variable, no further API change will be needed (other than relaxing the documented "pyodide must be globally-unique" constraint). I figure it's better to make this API change earlier rather than later.

It will be possible to completely remove the global variable dependence when Firefox implements support for using ES6 modules in webworkers (see https://bugzilla.mozilla.org/show_bug.cgi?id=1247687).
API Don't expose pyodide as a global variable in loadPyodide. For now, only one `pyodide` can be loaded in a given global scope because we need to use a global variable for package loading. This changes `loadPyodide` so that it no longer defines `globalThis.pyodide` in favor of just returning `pyodide` from `loadPyodide`. `Module` is placed on the global object as `globalThis.__pyodide_module` for the purposes of package loading. I added documentation to explicitly state that `loadPyodide` can only be run once in each global Javascript context, an error will be thrown otherwise.

This has two advantages: 
1. The returned `pyodide` module is understandable to Typescript and other code analysis, whereas the global variable is not understandable.
2. If in the future we are able to remove the global variable, no further API change will be needed (other than relaxing the documented "pyodide must be globally-unique" constraint). I figure it's better to make this API change earlier rather than later.

It will be possible to completely remove the global variable dependence when Firefox implements support for using ES6 modules in webworkers (see https://bugzilla.mozilla.org/show_bug.cgi?id=1247687).
<div align="center">
  <a href="https://github.com/pyodide/pyodide">
  <img src="./docs/_static/img/pyodide-logo-readme.png" alt="Pyodide">
  </a>
</div>


[![Build Status](https://circleci.com/gh/pyodide/pyodide.png)](https://circleci.com/gh/pyodide/pyodide)
[![Documentation Status](https://readthedocs.org/projects/pyodide/badge/?version=stable)](https://pyodide.readthedocs.io/?badge=stable)

Python with the scientific stack, compiled to WebAssembly.

## What is Pyodide?

Pyodide may be used in any context where you want to run Python inside a web
browser.

Pyodide brings the Python 3.8 runtime to the browser via WebAssembly, along with
the Python scientific stack including NumPy, Pandas, Matplotlib, SciPy, and
scikit-learn. The [packages directory](packages) lists over 75 packages which
are currently available. In addition it's possible to install pure Python wheels
from PyPi.

Pyodide provides transparent conversion of objects between Javascript and
Python. When used inside a browser, Python has full access to the Web APIs.

## Try Pyodide (no installation needed)

Try Pyodide in a
[REPL](https://pyodide.org/en/stable/console.html) directly in
your browser. For further information, see the
[documentation](https://pyodide.org/en/stable/).

## Getting Started

Pyodide offers three different ways to get started depending on your needs and
technical resources. These include:

- Use a hosted distribution of Pyodide: see the [Getting
  Started](https://pyodide.org/en/stable/usage/quickstart.html) documentation.
- Download a version of Pyodide from the [releases
  page](https://github.com/pyodide/pyodide/releases/) and serve it
  with a web server.
- [Build Pyodide from source](https://pyodide.org/en/stable/development/building-from-sources.html)
  - Build natively with `make`: primarily for Linux users who want to
    experiment or contribute back to the project.
  - [Use a Docker image](https://pyodide.org/en/stable/development/building-from-sources.html#using-docker):
    recommended for Windows and macOS users and for Linux users who prefer a
    Debian-based Docker image with the dependencies already installed.


## History
Pyodide was created in 2018 by [Michael Droettboom](https://github.com/mdboom)
at Mozilla as part of the [Iodide
project](https://github.com/iodide-project/iodide). Iodide is an experimental
web-based notebook environment for literate scientific computing and
communication.

Iodide is no longer maintained. If you want to use Pyodide in an interactive
client-side notebook, see [Pyodide notebook
environments](https://pyodide.org/en/stable/project/related-projects.html#notebook-environments-ides-repls).

## Contributing

Please view the [contributing
guide](https://pyodide.org/en/stable/development/contributing.html) for tips
on filing issues, making changes, and submitting pull requests. Pyodide is an
independent and community-driven open-source project. The decision making
process is outlined in the [Project
governance](https://pyodide.org/en/stable/project/governance.html).

## Communication

- Mailing list: [mail.python.org/mailman3/lists/pyodide.python.org/](https://mail.python.org/mailman3/lists/pyodide.python.org/)
- Gitter: [gitter.im/pyodide/community](https://gitter.im/pyodide/community)
- Twitter: [twitter.com/pyodide](https://twitter.com/pyodide)
- Stack Overflow: [stackoverflow.com/questions/tagged/pyodide](https://stackoverflow.com/questions/tagged/pyodide)

## License

Pyodide uses the [Mozilla Public License Version
2.0](https://choosealicense.com/licenses/mpl-2.0/).

<div align="center">
  <a href="https://github.com/pyodide/pyodide">
  <img src="./docs/_static/img/pyodide-logo-readme.png" alt="Pyodide">
  </a>
</div>


[![Build Status](https://circleci.com/gh/pyodide/pyodide.png)](https://circleci.com/gh/pyodide/pyodide)
[![Documentation Status](https://readthedocs.org/projects/pyodide/badge/?version=stable)](https://pyodide.readthedocs.io/?badge=stable)

Python with the scientific stack, compiled to WebAssembly.

## What is Pyodide?

Pyodide may be used in any context where you want to run Python inside a web
browser.

Pyodide brings the Python 3.8 runtime to the browser via WebAssembly, along with
the Python scientific stack including NumPy, Pandas, Matplotlib, SciPy, and
scikit-learn. The [packages directory](packages) lists over 75 packages which
are currently available. In addition it's possible to install pure Python wheels
from PyPi.

Pyodide provides transparent conversion of objects between Javascript and
Python. When used inside a browser, Python has full access to the Web APIs.

## Try Pyodide (no installation needed)

Try Pyodide in a
[REPL](https://pyodide.org/en/stable/console.html) directly in
your browser. For further information, see the
[documentation](https://pyodide.org/en/stable/).

## Getting Started

Pyodide offers three different ways to get started depending on your needs and
technical resources. These include:

- Use a hosted distribution of Pyodide: see the [Getting
  Started](https://pyodide.org/en/stable/usage/quickstart.html) documentation.
- Download a version of Pyodide from the [releases
  page](https://github.com/pyodide/pyodide/releases/) and serve it
  with a web server.
- [Build Pyodide from source](https://pyodide.org/en/stable/development/building-from-sources.html)
  - Build natively with `make`: primarily for Linux users who want to
    experiment or contribute back to the project.
  - [Use a Docker image](https://pyodide.org/en/stable/development/building-from-sources.html#using-docker):
    recommended for Windows and macOS users and for Linux users who prefer a
    Debian-based Docker image with the dependencies already installed.


## History
Pyodide was created in 2018 by [Michael Droettboom](https://github.com/mdboom)
at Mozilla as part of the [Iodide
project](https://github.com/iodide-project/iodide). Iodide is an experimental
web-based notebook environment for literate scientific computing and
communication.

Iodide is no longer maintained. If you want to use Pyodide in an interactive
client-side notebook, see [Pyodide notebook
environments](https://pyodide.org/en/stable/project/related-projects.html#notebook-environments-ides-repls).

## Contributing

Please view the [contributing
guide](https://pyodide.org/en/stable/development/contributing.html) for tips
on filing issues, making changes, and submitting pull requests. Pyodide is an
independent and community-driven open-source project. The decision making
process is outlined in the [Project
governance](https://pyodide.org/en/stable/project/governance.html).

## Communication

- Mailing list: [mail.python.org/mailman3/lists/pyodide.python.org/](https://mail.python.org/mailman3/lists/pyodide.python.org/)
- Gitter: [gitter.im/pyodide/community](https://gitter.im/pyodide/community)
- Twitter: [twitter.com/pyodide](https://twitter.com/pyodide)
- Stack Overflow: [stackoverflow.com/questions/tagged/pyodide](https://stackoverflow.com/questions/tagged/pyodide)

## License

Pyodide uses the [Mozilla Public License Version
2.0](https://choosealicense.com/licenses/mpl-2.0/).
