daachorse is a fast implementation of the Aho-Corasick algorithm using the compact double-array data structure. This is a Python wrapper.

Run the following command:

$ pip install daachorse

You need to install the Rust compiler following the documentation beforehand. daachorse uses pyproject.toml, so you also need to upgrade pip to version 19 or later.

$ pip install --upgrade pip

After setting up the environment, you can install daachorse as follows:

$ pip install git+https://github.com/daac-tools/python-daachorse

Daachorse contains some search options, ranging from basic matching with the Aho-Corasick algorithm to trickier matching. All of them will run very fast based on the double-array data structure and can be easily plugged into your application as shown below.

To search for all occurrences of registered patterns that allow for positional overlap in the input text, use find_overlapping(). When you instantiate a new automaton, unique identifiers are assigned to each pattern in the input order. The match result has the character positions of the occurrence and its identifier.

>> import daachorse
>> patterns = ['bcd', 'ab', 'a']
>> pma = daachorse.Automaton(patterns)
>> pma.find_overlapping('abcd')
[(0, 1, 2), (0, 2, 1), (1, 4, 0)]

If you do not want to allow positional overlap, use find() instead. It performs the search on the Aho-Corasick automaton and reports patterns first found in each iteration.

>> import daachorse
>> patterns = ['bcd', 'ab', 'a']
>> pma = daachorse.Automaton(patterns)
>> pma.find('abcd')
[(0, 1, 2), (1, 4, 0)]

If you want to search for the longest pattern without positional overlap in each iteration, use MATCH_KIND_LEFTMOST_LONGEST in the construction.

>> import daachorse
>> patterns = ['ab', 'a', 'abcd']
>> pma = daachorse.Automaton(patterns, daachorse.MATCH_KIND_LEFTMOST_LONGEST)
>> pma.find('abcd')
[(0, 4, 2)]

If you want to find the the earliest registered pattern among ones starting from the search position, use MATCH_KIND_LEFTMOST_FIRST.

This is so-called the leftmost first match, a bit tricky search option. For example, in the following code, ab is reported because it is the earliest registered one.

>> import daachorse
>> patterns = ['ab', 'a', 'abcd']
>> pma = daachorse.Automaton(patterns, daachorse.MATCH_KIND_LEFTMOST_FIRST)
>> pma.find('abcd')
[(0, 2, 0)]

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.