> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sourcery.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Use Dictionary Union

#### Sourcery refactoring id: `use-dictionary-union`

#### Description

Replace a sequence of unpacked dictionaries with a use of the dictionary union
operator.

#### Before

```python
tube_stops = {
    "Piccadilly": ["Heathrow", "King's Cross"],
    "Bakerloo": ["Baker Street", "Oxford Circus"],
}
bus_stops = {
    "65": ["Kingston Station", "Kew Bridge"],
}
all_stops = {**tube_stops, **bus_stops}
```

#### After

```python
tube_stops = {
    "Piccadilly": ["Heathrow", "King's Cross"],
    "Bakerloo": ["Baker Street", "Oxford Circus"],
}
bus_stops = {
    "65": ["Kingston Station", "Kew Bridge"],
}
all_stops = tube_stops | bus_stops
```

#### Explanation

The dictionary union operator was introduced in Python 3.9 (see
[PEP 584](https://peps.python.org/pep-0584/)). It provides an interface for
dictionaries similar to set unions, where the result combines the keys from both
dictionaries, with the right dictionary taking precedence in the case of
duplicates. This is clearer, more concise, and more discoverable than using
dictionary unpacking to create a new dictionary.

See also: [`dict-assign-update-to-union`](/reference/refactorings/python/dict-assign-update-to-union/)