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https://github.com/pytries/datrie

Fast, efficiently stored Trie for Python. Uses libdatrie.
https://github.com/pytries/datrie
Last synced: 3 days ago
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Fast, efficiently stored Trie for Python. Uses libdatrie.
Host: GitHub
URL: https://github.com/pytries/datrie
Owner: pytries
License: lgpl-2.1
Created: 2012-07-08T20:18:28.000Z (over 12 years ago)
Default Branch: master
Last Pushed: 2024-02-01T20:39:44.000Z (9 months ago)
Last Synced: 2024-10-11T14:49:06.382Z (about 1 month ago)
Language: Python
Homepage: http://pypi.python.org/pypi/datrie/
Size: 2.1 MB
Stars: 530
Watchers: 22
Forks: 88
Open Issues: 39
Metadata Files:
- Readme: README.rst
- Changelog: CHANGES.rst
- License: COPYING
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README

        datrie |travis| |appveyor|

==========================

.. |travis| image:: https://travis-ci.org/pytries/datrie.svg

   :target: https://travis-ci.org/pytries/datrie

.. |appveyor| image:: https://ci.appveyor.com/api/projects/status/6bpvhllpjhlau7x0?svg=true

   :target: https://ci.appveyor.com/project/superbobry/datrie

Super-fast, efficiently stored Trie for Python (2.x and 3.x).

Uses `libdatrie`_.

.. _libdatrie: https://linux.thai.net/~thep/datrie/datrie.html

Installation

============

::

    pip install datrie

Usage

=====

Create a new trie capable of storing items with lower-case ascii keys::

    >>> import string

    >>> import datrie

    >>> trie = datrie.Trie(string.ascii_lowercase)

``trie`` variable is a dict-like object that can have unicode keys of

certain ranges and Python objects as values.

In addition to implementing the mapping interface, tries facilitate

finding the items for a given prefix, and vice versa, finding the

items whose keys are prefixes of a given string. As a common special

case, finding the longest-prefix item is also supported.

.. warning::

    For efficiency you must define allowed character range(s) while

    creating trie. ``datrie`` doesn't check if keys are in allowed

    ranges at runtime, so be careful! Invalid keys are OK at lookup time

    but values won't be stored correctly for such keys.

Add some values to it (datrie keys must be unicode; the examples

are for Python 2.x)::

    >>> trie[u'foo'] = 5

    >>> trie[u'foobar'] = 10

    >>> trie[u'bar'] = 'bar value'

    >>> trie.setdefault(u'foobar', 15)

    10

Check if u'foo' is in trie::

    >>> u'foo' in trie

    True

Get a value::

    >>> trie[u'foo']

    5

Find all prefixes of a word::

    >>> trie.prefixes(u'foobarbaz')

    [u'foo', u'foobar']

    >>> trie.prefix_items(u'foobarbaz')

    [(u'foo', 5), (u'foobar', 10)]

    >>> trie.iter_prefixes(u'foobarbaz')

    

    >>> trie.iter_prefix_items(u'foobarbaz')

    

Find the longest prefix of a word::

    >>> trie.longest_prefix(u'foo')

    u'foo'

    >>> trie.longest_prefix(u'foobarbaz')

    u'foobar'

    >>> trie.longest_prefix(u'gaz')

    KeyError: u'gaz'

    >>> trie.longest_prefix(u'gaz', default=u'vasia')

    u'vasia'

    >>> trie.longest_prefix_item(u'foobarbaz')

    (u'foobar', 10)

Check if the trie has keys with a given prefix::

    >>> trie.has_keys_with_prefix(u'fo')

    True

    >>> trie.has_keys_with_prefix(u'FO')

    False

Get all items with a given prefix from a trie::

    >>> trie.keys(u'fo')

    [u'foo', u'foobar']

    >>> trie.items(u'ba')

    [(u'bar', 'bar value')]

    >>> trie.values(u'foob')

    [10]

Get all suffixes of certain word starting with a given prefix from a trie::

    >>> trie.suffixes()

    [u'pro', u'producer', u'producers', u'product', u'production', u'productivity', u'prof']

    >>> trie.suffixes(u'prod')

    [u'ucer', u'ucers', u'uct', u'uction', u'uctivity']

Save & load a trie (values must be picklable)::

    >>> trie.save('my.trie')

    >>> trie2 = datrie.Trie.load('my.trie')

Trie and BaseTrie

=================

There are two Trie classes in datrie package: ``datrie.Trie`` and

``datrie.BaseTrie``. ``datrie.BaseTrie`` is slightly faster and uses less

memory but it can store only integer numbers -2147483648 <= x <= 2147483647.

``datrie.Trie`` is a bit slower but can store any Python object as a value.

If you don't need values or integer values are OK then use ``datrie.BaseTrie``::

    import datrie

    import string

    trie = datrie.BaseTrie(string.ascii_lowercase)

Custom iteration

================

If the built-in trie methods don't fit you can use ``datrie.State`` and

``datrie.Iterator`` to implement custom traversal.

.. note::

    If you use ``datrie.BaseTrie`` you need ``datrie.BaseState`` and

    ``datrie.BaseIterator`` for custom traversal.

For example, let's find all suffixes of ``'fo'`` for our trie and get

the values::

    >>> state = datrie.State(trie)

    >>> state.walk(u'foo')

    >>> it = datrie.Iterator(state)

    >>> while it.next():

    ...     print(it.key())

    ...     print(it.data))

    o

    5

    obar

    10

Performance

===========

Performance is measured for ``datrie.Trie`` against Python's dict with

100k unique unicode words (English and Russian) as keys and '1' numbers

as values.

``datrie.Trie`` uses about 5M memory for 100k words; Python's dict

uses about 22M for this according to my unscientific tests.

This trie implementation is 2-6 times slower than python's dict

on __getitem__. Benchmark results (macbook air i5 1.8GHz,

"1.000M ops/sec" == "1 000 000 operations per second")::

    Python 2.6:

    dict __getitem__: 7.107M ops/sec

    trie __getitem__: 2.478M ops/sec

    Python 2.7:

    dict __getitem__: 6.550M ops/sec

    trie __getitem__: 2.474M ops/sec

    Python 3.2:

    dict __getitem__: 8.185M ops/sec

    trie __getitem__: 2.684M ops/sec

    Python 3.3:

    dict __getitem__: 7.050M ops/sec

    trie __getitem__: 2.755M ops/sec

Looking for prefixes of a given word is almost as fast as

``__getitem__`` (results are for Python 3.3)::

    trie.iter_prefix_items (hits):      0.461M ops/sec

    trie.prefix_items (hits):           0.743M ops/sec

    trie.prefix_items loop (hits):      0.629M ops/sec

    trie.iter_prefixes (hits):          0.759M ops/sec

    trie.iter_prefixes (misses):        1.538M ops/sec

    trie.iter_prefixes (mixed):         1.359M ops/sec

    trie.has_keys_with_prefix (hits):   1.896M ops/sec

    trie.has_keys_with_prefix (misses): 2.590M ops/sec

    trie.longest_prefix (hits):         1.710M ops/sec

    trie.longest_prefix (misses):       1.506M ops/sec

    trie.longest_prefix (mixed):        1.520M ops/sec

    trie.longest_prefix_item (hits):    1.276M ops/sec

    trie.longest_prefix_item (misses):  1.292M ops/sec

    trie.longest_prefix_item (mixed):   1.379M ops/sec

Looking for all words starting with a given prefix is mostly limited

by overall result count (this can be improved in future because a

lot of time is spent decoding strings from utf_32_le to Python's

unicode)::

    trie.items(prefix="xxx"), avg_len(res)==415:        0.609K ops/sec

    trie.keys(prefix="xxx"), avg_len(res)==415:         0.642K ops/sec

    trie.values(prefix="xxx"), avg_len(res)==415:       4.974K ops/sec

    trie.items(prefix="xxxxx"), avg_len(res)==17:       14.781K ops/sec

    trie.keys(prefix="xxxxx"), avg_len(res)==17:        15.766K ops/sec

    trie.values(prefix="xxxxx"), avg_len(res)==17:      96.456K ops/sec

    trie.items(prefix="xxxxxxxx"), avg_len(res)==3:     75.165K ops/sec

    trie.keys(prefix="xxxxxxxx"), avg_len(res)==3:      77.225K ops/sec

    trie.values(prefix="xxxxxxxx"), avg_len(res)==3:    320.755K ops/sec

    trie.items(prefix="xxxxx..xx"), avg_len(res)==1.4:  173.591K ops/sec

    trie.keys(prefix="xxxxx..xx"), avg_len(res)==1.4:   180.678K ops/sec

    trie.values(prefix="xxxxx..xx"), avg_len(res)==1.4: 503.392K ops/sec

    trie.items(prefix="xxx"), NON_EXISTING:             2023.647K ops/sec

    trie.keys(prefix="xxx"), NON_EXISTING:              1976.928K ops/sec

    trie.values(prefix="xxx"), NON_EXISTING:            2060.372K ops/sec

Random insert time is very slow compared to dict, this is the limitation

of double-array tries; updates are quite fast. If you want to build a trie,

consider sorting keys before the insertion::

    dict __setitem__ (updates):            6.497M ops/sec

    trie __setitem__ (updates):            2.633M ops/sec

    dict __setitem__ (inserts, random):    5.808M ops/sec

    trie __setitem__ (inserts, random):    0.053M ops/sec

    dict __setitem__ (inserts, sorted):    5.749M ops/sec

    trie __setitem__ (inserts, sorted):    0.624M ops/sec

    dict setdefault (updates):             3.455M ops/sec

    trie setdefault (updates):             1.910M ops/sec

    dict setdefault (inserts):             3.466M ops/sec

    trie setdefault (inserts):             0.053M ops/sec

Other results (note that ``len(trie)`` is currently implemented

using trie traversal)::

    dict __contains__ (hits):    6.801M ops/sec

    trie __contains__ (hits):    2.816M ops/sec

    dict __contains__ (misses):  5.470M ops/sec

    trie __contains__ (misses):  4.224M ops/sec

    dict __len__:                334336.269 ops/sec

    trie __len__:                22.900 ops/sec

    dict values():               406.507 ops/sec

    trie values():               20.864 ops/sec

    dict keys():                 189.298 ops/sec

    trie keys():                 2.773 ops/sec

    dict items():                48.734 ops/sec

    trie items():                2.611 ops/sec

Please take this benchmark results with a grain of salt; this

is a very simple benchmark and may not cover your use case.

Current Limitations

===================

* keys must be unicode (no implicit conversion for byte strings

  under Python 2.x, sorry);

* there are no iterator versions of keys/values/items (this is not

  implemented yet);

* it is painfully slow and maybe buggy under pypy;

* library is not tested with narrow Python builds.

Contributing

============

Development happens at github: https://github.com/pytries/datrie.

Feel free to submit ideas, bugs, pull requests.

Running tests and benchmarks

----------------------------

Make sure `tox`_ is installed and run

::

    $ tox

from the source checkout. Tests should pass under Python 2.7 and 3.4+.

::

    $ tox -c tox-bench.ini

runs benchmarks.

If you've changed anything in the source code then

make sure `cython`_ is installed and run

::

    $ update_c.sh

before each ``tox`` command.

Please note that benchmarks are not included in the release

tar.gz's because benchmark data is large and this

saves a lot of bandwidth; use source checkouts from

github or bitbucket for the benchmarks.

.. _cython: https://cython.org/

.. _tox: https://tox.readthedocs.io/

Authors & Contributors

----------------------

See https://github.com/pytries/datrie/graphs/contributors.

This module is based on `libdatrie`_ C library by Theppitak Karoonboonyanan

and is inspired by `fast_trie`_ Ruby bindings, `PyTrie`_ pure

Python implementation and `Tree::Trie`_ Perl implementation;

some docs and API ideas are borrowed from these projects.

.. _fast_trie: https://github.com/tyler/trie

.. _PyTrie: https://github.com/gsakkis/pytrie

.. _Tree::Trie: https://metacpan.org/pod/release/AVIF/Tree-Trie-1.9/Trie.pm

License

=======

Licensed under LGPL v2.1.