The bidirectional mapping library for Python.

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  • has been used for many years by several teams at Google, Venmo, CERN, Bank of America Merrill Lynch, Bloomberg, Two Sigma, and many others
  • has carefully designed APIs for safety, simplicity, flexibility, and ergonomics
  • is fast, lightweight, and has no runtime dependencies other than Python’s standard library
  • integrates natively with Python’s interfaces
  • provides type hints for all public APIs
  • is implemented in concise, well-factored, pure (PyPy-compatible) Python code that is optimized for running efficiently as well as for reading and learning [1]
  • has extensive docs and test coverage (including property-based tests and benchmarks) run continuously on all supported Python versions


pip install bidict

Quick Start

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

For more usage documentation, head to the Introduction [3] and proceed from there.

Voluntary Community Support


Please feel free to leave a message in the bidict chatroom or open a new issue on GitHub for voluntary community support. You can search through existing issues before creating a new one in case your issue has been addressed already.

Enterprise Support

Enterprise support via Tidelift

Enterprise-level support for bidict can be obtained via the Tidelift subscription.

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:


See the Changelog [2] for a history of notable changes to bidict.

Release Notifications

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Watch releases on GitHub or to be notified when new versions of bidict are released.

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 Learning from bidict [1] if you’re interested in learning more.


bidict is currently a one-person operation maintained on a voluntary basis.

Your help would be most welcome! See the Contributors’ Guide [4] for more information.


Sponsor through GitHub

Bidict is the product of thousands of hours of my unpaid work over the 12+ years I’ve been maintaining it.

If bidict has helped you accomplish your work, especially work you’ve been paid for, it’s easy to sponsor me through GitHub.

Choose a tier and GitHub handles everything else. The sponsorship just goes on your regular GitHub bill; there’s nothing extra to do. You can also sponsor me through Gumroad or PayPal.

Read more about companies supporting open source developers.

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:

[1](1, 2) docs/learning-from-bidict.rst |
[2]CHANGELOG.rst |
[3](1, 2) docs/intro.rst |
[4]docs/contributors-guide.rst |

Next: Introduction [3]