datrie |travis| |appveyor|
==========================

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   :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')
    <generator object ...>

    >>> trie.iter_prefix_items(u'foobarbaz')
    <generator object ...>

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.