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Dictionaries & sets

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

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Dictionaries & sets easy

How to swap dict keys and values in Python when values are unique

Swap dict keys and values using a dict comprehension, with a guard that raises an error when values repeat.

dictionary comprehension keys-values
Python 
def swap_dict_keys_values(d):
    """Swap keys and values in a dict, assuming values are unique."""
    if len(set(d.values())) != len(d.values()):
        raise ValueError("Values must be unique to swap keys and values")
    return {v: k for k, v in d.items()}

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