retrie 0.3.1

Efficient Trie-based regex unions for blacklist/whitelist filtering and one-pass mapping-based string replacing

retrie

retrie offers fast methods to match and replace (sequences of) strings based on efficient Trie-based regex unions.

Trie

Instead of matching against a simple regex union, which becomes slow for large sets of words, a more efficient regex pattern can be compiled using a Trie structure:

from retrie.trie import Trie


trie = Trie()

trie.add("abc", "foo", "abs")
assert trie.pattern() == "(?:ab[cs]|foo)"  # equivalent to but faster than "(?:abc|abs|foo)"

trie.add("absolute")
assert trie.pattern() == "(?:ab(?:c|s(?:olute)?)|foo)"

trie.add("abx")
assert trie.pattern() == "(?:ab(?:[cx]|s(?:olute)?)|foo)"

trie.add("abxy")
assert trie.pattern() == "(?:ab(?:c|s(?:olute)?|xy?)|foo)"

A Trie may be populated with zero or more strings at instantiation or via Trie.add, from which method chaining is possible. Two instances can be merged with the + (new instance) and += (in-place update) operators. Instances will compare equal if their data dictionaries are equal.

trie = Trie()
trie += Trie("abc")
assert (
    trie + Trie().add("foo")
    == Trie("abc", "foo")
    == Trie(*["abc", "foo"])
    == Trie().add(*["abc", "foo"])
    == Trie().add("abc", "foo")
    == Trie().add("abc").add("foo")
)

Installation

This pure-Python, OS independent package is available on PyPI:

$ pip install retrie

Usage

For documentation, see retrie.readthedocs.io.

The following objects are all subclasses of retrie.retrie.Retrie, which handles filling the Trie and compiling the corresponding regex pattern.

Blacklist

The Blacklist object can be used to filter out bad occurences in a text or a sequence of strings:

from retrie.retrie import Blacklist

# check out docstrings and methods
help(Blacklist)

blacklist = Blacklist(["abc", "foo", "abs"], match_substrings=False)
blacklist.compiled
# re.compile(r'(?<=\b)(?:ab[cs]|foo)(?=\b)', re.IGNORECASE|re.UNICODE)
assert not blacklist.is_blacklisted("a foobar")
assert tuple(blacklist.filter(("good", "abc", "foobar"))) == ("good", "foobar")
assert blacklist.cleanse_text(("good abc foobar")) == "good  foobar"

blacklist = Blacklist(["abc", "foo", "abs"], match_substrings=True)
blacklist.compiled
# re.compile(r'(?:ab[cs]|foo)', re.IGNORECASE|re.UNICODE)
assert blacklist.is_blacklisted("a foobar")
assert tuple(blacklist.filter(("good", "abc", "foobar"))) == ("good",)
assert blacklist.cleanse_text(("good abc foobar")) == "good  bar"

Whitelist

Similar methods are available for the Whitelist object:

from retrie.retrie import Whitelist

# check out docstrings and methods
help(Whitelist)

whitelist = Whitelist(["abc", "foo", "abs"], match_substrings=False)
whitelist.compiled
# re.compile(r'(?<=\b)(?:ab[cs]|foo)(?=\b)', re.IGNORECASE|re.UNICODE)
assert not whitelist.is_whitelisted("a foobar")
assert tuple(whitelist.filter(("bad", "abc", "foobar"))) == ("abc",)
assert whitelist.cleanse_text(("bad abc foobar")) == "abc"

whitelist = Whitelist(["abc", "foo", "abs"], match_substrings=True)
whitelist.compiled
# re.compile(r'(?:ab[cs]|foo)', re.IGNORECASE|re.UNICODE)
assert whitelist.is_whitelisted("a foobar")
assert tuple(whitelist.filter(("bad", "abc", "foobar"))) == ("abc", "foobar")
assert whitelist.cleanse_text(("bad abc foobar")) == "abcfoo"

Replacer

The Replacer object does a fast single-pass search & replace for occurrences of replacement_mapping.keys() with corresponding values.

from retrie.retrie import Replacer

# check out docstrings and methods
help(Replacer)

replacement_mapping = dict(zip(["abc", "foo", "abs"], ["new1", "new2", "new3"]))

replacer = Replacer(replacement_mapping, match_substrings=True)
replacer.compiled
# re.compile(r'(?:ab[cs]|foo)', re.IGNORECASE|re.UNICODE)
assert replacer.replace("ABS ...foo... foobar") == "new3 ...new2... new2bar"

replacer = Replacer(replacement_mapping, match_substrings=False)
replacer.compiled
# re.compile(r'\b(?:ab[cs]|foo)\b', re.IGNORECASE|re.UNICODE)
assert replacer.replace("ABS ...foo... foobar") == "new3 ...new2... foobar"

replacer = Replacer(replacement_mapping, match_substrings=False, re_flags=None)
replacer.compiled  # on py3, re.UNICODE is always enabled
# re.compile(r'\b(?:ab[cs]|foo)\b')
assert replacer.replace("ABS ...foo... foobar") == "ABS ...new2... foobar"

replacer = Replacer(replacement_mapping, match_substrings=False, word_boundary=" ")
replacer.compiled
# re.compile(r'(?<= )(?:ab[cs]|foo)(?= )', re.IGNORECASE|re.UNICODE)
assert replacer.replace(". ABS ...foo... foobar") == ". new3 ...foo... foobar"

Development

Run make help for options like installing for development, linting and testing.