Bidict Save

The bidirectional mapping library for Python.

Project README

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The bidirectional mapping library for Python.


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  • Depended on by Google, Venmo, CERN, Baidu, Tencent, and teams across the world since 2009

  • Familiar, Pythonic APIs that are carefully designed for safety, simplicity, flexibility, and ergonomics

  • Lightweight, with no runtime dependencies outside Python's standard library

  • Implemented in concise, well-factored, fully type-hinted Python code that is optimized for running efficiently as well as for long-term maintenance and stability (not to mention joy <#learning-from-bidict>__ :)

  • Extensively documented <>__

  • 100% test coverage running continuously across all supported Python versions


pip install bidict

Quick Start

.. code:: python

from bidict import bidict element_by_symbol = bidict({'H': 'hydrogen'}) element_by_symbol['H'] 'hydrogen' element_by_symbol.inverse['hydrogen'] 'H'

For more usage documentation, head to the :doc:intro [#fn-intro]_ and proceed from there.

Enterprise Support

Enterprise-level support for bidict can be obtained via the Tidelift subscription <>__ or by contacting me directly <mailto:[email protected]>__.

I have a US-based LLC set up for invoicing, and I have 15+ years of professional experience delivering software and support to companies successfully.

You can also sponsor my work through platforms like GitHub Sponsors. See the Sponsoring <#sponsoring>__ section below for details, including rationale and examples of companies supporting the open source projects they depend on.

Voluntary Community Support

Please search through already-asked questions and answers in GitHub Discussions <>__ and the issue tracker <>__ in case your question has already been addressed.

Otherwise, please feel free to start a new discussion <>__ or create a new issue <>__ on GitHub, or ask in the bidict chatroom <>__ for voluntary community support.

Notice of Usage

If you use bidict, and especially if your usage or your organization is significant in some way, please let me know in any of the following ways:

  • star bidict on GitHub <>__
  • post in GitHub Discussions <>__
  • leave a message in the chat room <>__
  • email me <mailto:[email protected]>__


For bidict release notes, see the :doc:changelog. [#fn-changelog]_

Release Notifications

.. duplicated in CHANGELOG.rst: (would use .. include:: but GitHub doesn't understand it)

Watch bidict releases on GitHub <>__ to be notified when new versions of bidict are published. Click the "Watch" dropdown, choose "Custom", and then choose "Releases".

Learning from bidict

One of the best things about bidict is that it touches a surprising number of interesting Python corners, especially given its small size and scope.

Check out :doc:learning-from-bidict [#fn-learning]_ if you're interested in learning more.


I have been bidict's sole maintainer and active contributor <>__ since I started the project ~15 years ago.

Your help would be most welcome! See the :doc:contributors-guide [#fn-contributing]_ for more information.


.. duplicated in CONTRIBUTING.rst (would use .. include:: but GitHub doesn't understand it)

.. image:: :target: :alt: Sponsor through GitHub

.. image:: :target: :alt: Sponsors on GitHub

Bidict is the product of thousands of hours of my unpaid work over the ~15 years that I've been the sole maintainer.

If bidict has helped you or your company accomplish your work, please sponsor my work through GitHub <>__ and/or ask your company to do the same.

Choose a tier and GitHub handles everything else. Your GitHub sponsorship will automatically go on the same bill you already have set up with GitHub, so after the one-click signup, there's nothing else to do.

See the following for rationale and examples of companies supporting the open source projects they depend on in this manner:

  • <>__
  • <>__
  • <>__

.. - <>__ .. - <>__ .. - <>__ .. - <>__

You can also support my work through Gumroad <>__ or PayPal <>, or through a support engagement with my LLC. See Enterprise Support <#enterprise-support> above for details.

Finding Documentation

If you're viewing this on <>__, note that multiple versions of the documentation are available, and you can choose a different version using the popup menu at the bottom-right. Please make sure you're viewing the version of the documentation that corresponds to the version of bidict you'd like to use.

If you're viewing this on GitHub, PyPI, or some other place that can't render and link this documentation properly and are seeing broken links, try these alternate links instead:

.. [#fn-intro] <>__ | <docs/intro.rst>__

.. [#fn-changelog] <>__ | <CHANGELOG.rst>__

.. [#fn-learning] <>__ | <docs/learning-from-bidict.rst>__

.. [#fn-contributing] <>__ | <CONTRIBUTING.rst>__

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