Reference library

Dictionaries & sets

Key–value maps, uniqueness, counting, grouping, and fast lookups.

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Dictionaries & sets easy

How to Invert a Dictionary in Python Safely

Swap dictionary keys and values while detecting duplicate values to prevent silent data loss.

dictionary inversion data-safety
Python 
def invert_dict_safely(d):
    inverted = {}
    for key, value in d.items():
        if value not in inverted:
            inverted[value] = key
        else:
            raise ValueError(f"Duplicate value '{value}' would cause data loss")
    return inverted


if __name__ == "__main__":
    sample = {"a": 1, "b": 2,…
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