Python Multi-modal String Search Aho-Corasick Detailed Explanation

Yes in PythonpyahocorasickA class provided by the library to implement the Aho-Corasick automaton. The Aho-Corasick algorithm is an efficient algorithm for precise or approximate multi-modal string search.

passpip install pyahocorasickInstallpyahocorasicklibrary.
Moreover, the module is written in C, and a C compiler is required to compile the native Cpython extension during installation.

useThe general steps of the class are as follows:

ImportahocorasickLibrary:import ahocorasick。
createAutomatonObject:a = () 。
(Optional) Add string keys and their associated values to the automaton, which can be used as a trie tree. For example:

for idx, key in enumerate('heherhersshe'.split()):
    a.add_word(key, (idx, key))

Callmake_automaton()The method completes and creates the Aho-Corasick automaton:a.make_automaton() 。

After creating the automaton, you can use the following main methods to search:

iter(string, (start, (end))): Perform the Aho-Corasick search process using the provided input string. It returns an iterator that returns tuples for keys found in the string(end_index, value),inend_indexis the index position that matches the end.valueis the value associated with the matching key.
iter_long(string, (start, (end))): Returns an iterator that searches for the longest, non-overlapping match (automaton_search_iter_longclass object).

The following is a useSample code for multi-modal string search:

import ahocorasick as ah
a = ()
with open('', 'r', encoding='utf-8') as f2:  # Load the file    keywords = (() for a in ())  # Load keywords    # Use the add_word method to add keywords to the automaton!    for x in range(len(keywords)):
        a.add_word(keywords[x], (x, keywords[x]))  # The second parameter is a custom return value# Create aho-corasick automatona.make_automaton()
with open('', 'r', encoding='utf-8') as f:  # Open the document to be retrieved    jianjie = ()  # Read the body (if there are too many, you can break the load and search in segments)# Start searching, this method matches the longest stringfor item in a.iter_long(jianjie):
    print(item)
print('-' * 20)
# Start searching, this method matches all stringsfor item in (jianjie):
    print(item)

In the above example, first, an automaton object is createda, then read the keywords from the file and useadd_wordMethods Add keywords to the automaton. Then callmake_automatonMethod to create an Aho-Corasick automaton. Finally, read the body to search by opening another file and useiter_longanditerThe method performs matching search and prints the matching results.

The advantages of the Aho-Corasick automaton include the ability to find all strings for a given set in one run, suitable for scenarios where multi-modal string matching, such as network content filtering, copyright detection, virus scanning, etc., finding specific vocabulary or pattern in natural language processing, and finding specific sequence patterns in DNA or protein sequence analysis in bioinformatics.

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