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A dictionary that is indexed by insertion order.

Project Description

Build status

Introduction

indexed.IndexedOrderedDict is fully compatible with collections.OrderedDict and can be used as a drop in replacement. The main difference is that key, value and item views support accessing elements by their index.

d = indexed.IndexedOrderedDict()
d["first-key"] = "first-value"
d["second-key"] = "second-value"
d["third-key"] = "third-value"

values = d.values()
assert values[2] == "third-value"

assert d.keys().index("second-key") == 1

Features

  • Can be used with both Python 2 and 3. Provides keysview(), valuesview() and itemsview() which were removed from Python 3 for compability.
  • Access keys, values and items by index, e.g. d.keys()[5].
  • Find the index of a key, e.g. d.keys().index("key").

Excluding those additions the API is the same as the API of collections.OrderedDict(). Including:

  • Initializing, setting, getting and deleting items
  • Iterating forwards and in reverse
  • d.clear()
  • d.popitem(last=True)
  • d.move_to_end(key, last=True)
  • d.keys(), d.values(), d.items()
  • d.pop(key[, default])
  • d.setdefault(key, default=None)
  • String representation
  • Pickling
  • Copying
  • Creating from keys
  • Comparing order sensitively with other ordered dictionaries or order insensitively with standard mappings

Installing

The only dependencies are Python >= 2.7 or Python >= 3.0.

  • With pip:

    sudo pip install indexed.py
    
  • With easy_install:

    sudo easy_install indexed.py
    
  • From current source code:

    python setup.py build
    sudo python setup.py install
    

Performance

Performance is practically on the same order of magnitude as the built in collections.OrderedDict.

d collections.OrderedDict indexed.IndexedOrderedDict
Operation Avergage Worst case Average Worst case
d.copy() O(n) O(n) O(n) O(n)
d[key] O(1) O(n) O(1) O(n)
d[key] = value O(1) O(n) [1] O(1) O(n) [1]
del d[key] O(1) O(n) O(n) O(n)
d.keys()[i] O(n) [2] O(n) [2] O(1) O(1)
d.values()[i] O(n) [3] O(n) [3] O(1) O(n)
d.items()[i] O(n) [3] O(n) [3] O(1) O(n)
d.keys().index(x) O(n) [3] O(n) [3] O(n) O(n)
[1](1, 2) These are amortized worst case runtimes.
[2](1, 2) This does not work in Python 3 because colections.KeysView is not indexable. One of the theoretically best work arounds is next(itertools.islice(d.keys(), i, i + 1)).
[3](1, 2, 3, 4, 5, 6) Assuming the theoretically best possible workaround.

License

indexed.py is licensed under the GPL3. See the LICENSE file for full copyright and license information.

Release history Release notifications

This version
History Node

0.0.1

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Filename, size & hash SHA256 hash help File type Python version Upload date
indexed.py-0.0.1.tar.gz (16.9 kB) Copy SHA256 hash SHA256 Source None Sep 6, 2013

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