Bi-directional Dictionary in Python

See Python: Tips and Tricks for similar articles.

Here’s a quick function for creating a bi-directional dictionary in Python:

def bidict(d):
    d2 = d.copy()
    for k, v in d.items():
        if v in d2.keys():
            raise KeyError(
                "Cannot create bidirectional dict."
                + "Either d has a value that is the same as one of "
                + "its keys or multiple keys have the same value."
        d2[v] = k
    return d2

hellos = {
    "Chinese": "你好世界",
    "Dutch": "Hello wereld",
    "English": "Hello world",
    "French": "Bonjour monde",
    "German": "Hallo Welt",
    "Greek": "γειά σου κόσμος",
    "Italian": "Ciao mondo",
    "Japanese": "こんにちは世界",
    "Korean": "여보세요 세계",
    "Portuguese": "Olá mundo",
    "Russian": "Здравствулте мир",
    "Spanish": "Hola mundo",


If your original dictionary has two keys with the same value or has a value that is the same as one its keys, a KeyError will be thrown.

The new dict will look like this:

    "Bonjour monde": "French",
    "Chinese": "你好世界",
    "Ciao mondo": "Italian",
    "Dutch": "Hello wereld",
    "English": "Hello world",
    "French": "Bonjour monde",
    "German": "Hallo Welt",
    "Greek": "γειά σου κόσμος",
    "Hallo Welt": "German",
    "Hello wereld": "Dutch",
    "Hello world": "English",
    "Hola mundo": "Spanish",
    "Italian": "Ciao mondo",
    "Japanese": "こんにちは世界",
    "Korean": "여보세요 세계",
    "Olá mundo": "Portuguese",
    "Portuguese": "Olá mundo",
    "Russian": "Здравствулте мир",
    "Spanish": "Hola mundo",
    "γειά σου κόσμος": "Greek",
    "Здравствулте мир": "Russian",
    "こんにちは世界": "Japanese",
    "你好世界": "Chinese",
    "여보세요 세계": "Korean",

If you’re looking for something a little more robust, check out the bidict library.

Written by Nat Dunn. Follow Nat on Twitter.

Related Articles

  1. Fixing WebVTT Times with Python
  2. Using Python to Convert Images to WEBP
  3. Scientific Notation in Python
  4. Understanding Python’s __main__ variable
  5. Converting Leading Tabs to Spaces with Python
  6. pow(x, y, z) more efficient than x**y % z and other options
  7. A Python Model for Ping Pong Matches
  8. Bulk Convert Python files to IPython Notebook Files (py to ipynb conversion)
  9. Python’s date.strftime() slower than str(), split, unpack, and concatenate?
  10. Basic Python Programming Exercise: A Penny Doubled Every Day
  11. Bi-directional Dictionary in Python (this article)
  12. How to find all your Python installations on Windows (and Mac)
  13. Associate Python Files with IDLE
  14. Change Default autosave Interval in JupyterLab
  15. Python: isdigit() vs. isdecimal()
  16. Python Clocks Explained
  17. Python Color Constants Module
  18. Maximum recursion depth exceeded while calling a Python object
  19. When to use Static Methods in Python? Never
  20. Finally, a use case for finally – Python Exception Handling
  21. Creating an Email Decorator with Python and AWS
  22. Python Coding Challenge: Two People with the Same Birthday
  23. How to Create a Simple Simulation in Python – Numeric Data
  24. Collatz Conjecture in Python
  25. Simple Python Script for Extracting Text from an SRT File
  26. Python Virtual Environments with venv
  27. Mapping python to Python 3 on Your Mac
  28. How to Make IDLE the Default Editor for Python Files on Windows
  29. How to Do Ternary Operator Assignment in Python
  30. How to Convert Seconds to Years with Python
  31. How to Create a Python Package
  32. How to Read a File with Python
  33. How to Check the Operating System with Python
  34. How to Use enumerate() to Print a Numbered List in Python
  35. How to Repeatedly Append to a String in Python
  36. Checking your Sitemap for Broken Links with Python
  37. How to do Simultaneous Assignment in Python
  38. Visual Studio Code - Opening Files with Python open()
  39. How to Slice Strings in Python
  40. How Python Finds Imported Modules
  41. How to Merge Dictionaries in Python
  42. How to Index Strings in Python
  43. How to Create a Tuple in Python