listmap

Adapted from the collections.ChainMap class. A ListMap is a dict-like object that creates a single, updateable view of a list of dicts or other mappings.

The underlying list of mappings can be accessed and modified using the maps property, and the append method.

Main differences with ChainMap objects:

• Lookups search the underlying mappings starting from the last mapping and going backward in the list of mappings until a key is found.
• Lookups search the mappings from right to left (starting from the last mapping in the list and going backward) until a key is found
• Updates and deletions of keys operate on the last mapping in the list
• The append(m) method appends a new mapping m to the list
• The extend(iterable) method extends the mappings by appending mappings from iterable

Examples

These examples are adapted from the ChainMap docs to show the differences.

>>> baseline = {'music': 'bach', 'art': 'rembrandt'}
>>> adjustments = {'art': 'van gogh', 'opera': 'carmen'}
>>> list(ChainMap(adjustments, baseline))
['music', 'art', 'opera']

>>> list(ListMap(baseline, adjustments))
['music', 'art', 'opera']

The iteration order of a ListMap is the same ordering as a series of dict.update() calls starting from the first mapping in the list:

>>> combined = baseline.copy()
>>> combined.update(adjustments)
>>> list(combined)
['music', 'art', 'opera']

Contributing

This is an OPEN Source Project so please help out by reporting bugs or forking and opening pull requests when possible.

License

Copyright (c) 2020, Simone Marsili. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

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