Source code for cltk.prosody.lat.metrical_validator

"""Utility class for validating scansion patterns: hexameter, hendecasyllables, pentameter.
Allows users to configure the scansion symbols internally via a constructor argument;
a suitable default is provided."""

import logging
from typing import List

from Levenshtein import distance

from cltk.prosody.lat.scansion_constants import ScansionConstants

LOG = logging.getLogger(__name__)
LOG.addHandler(logging.NullHandler())

__author__ = ["Todd Cook <todd.g.cook@gmail.com>"]
__license__ = "MIT License"


[docs]class MetricalValidator: """Currently supports validation for: hexameter, hendecasyllables, pentameter."""
[docs] def is_valid_hexameter(self, scanned_line: str) -> bool: """Determine if a scansion pattern is one of the valid hexameter metrical patterns :param scanned_line: a line containing a sequence of stressed and unstressed syllables :return bool >>> print(MetricalValidator().is_valid_hexameter("-UU---UU---UU-U")) True """ line = scanned_line.replace(self.constants.FOOT_SEPARATOR, "") line = line.replace(" ", "") if len(line) < 12: return False line = line[:-1] + self.constants.OPTIONAL_ENDING return self.VALID_HEXAMETERS.__contains__(line)
[docs] def is_valid_hendecasyllables(self, scanned_line: str) -> bool: """Determine if a scansion pattern is one of the valid Hendecasyllables metrical patterns :param scanned_line: a line containing a sequence of stressed and unstressed syllables >>> print(MetricalValidator().is_valid_hendecasyllables("-U-UU-U-U-U")) True """ line = scanned_line.replace(self.constants.FOOT_SEPARATOR, "") line = line.replace(" ", "") if len(line) < 11: return False line = line[:-1] + self.constants.OPTIONAL_ENDING return self.VALID_HENDECASYLLABLES.__contains__(line)
[docs] def is_valid_pentameter(self, scanned_line: str) -> bool: """Determine if a scansion pattern is one of the valid Pentameter metrical patterns :param scanned_line: a line containing a sequence of stressed and unstressed syllables :return bool: whether or not the scansion is a valid pentameter >>> print(MetricalValidator().is_valid_pentameter('-UU-UU--UU-UUX')) True """ line = scanned_line.replace(self.constants.FOOT_SEPARATOR, "") line = line.replace(" ", "") if len(line) < 10: return False line = line[:-1] + self.constants.OPTIONAL_ENDING return self.VALID_PENTAMETERS.__contains__(line)
def __init__(self, constants=ScansionConstants()): self.constants = constants self.VALID_HEXAMETERS = [ self._build_hexameter_template(bin(x)[3:]) for x in range(32, 64) ] self.VALID_HENDECASYLLABLES = self._build_hendecasyllable_templates() self.VALID_PENTAMETERS = self._build_pentameter_templates()
[docs] def hexameter_feet(self, scansion: str) -> List[str]: """ Produces a list of hexameter feet, stressed and unstressed syllables with spaces intact. If the scansion line is not entirely correct, it will attempt to corral one or more improper patterns into one or more feet. :param: scansion, the scanned line :return list of strings, representing the feet of the hexameter, or if the scansion is wildly incorrect, the function will return an empty list. >>> print("|".join(MetricalValidator().hexameter_feet( ... "- U U - - - - - - - U U - U")).strip() ) - U U |- - |- - |- - |- U U |- U >>> print("|".join(MetricalValidator().hexameter_feet( ... "- U U - - U - - - - U U - U")).strip()) - U U |- - |U - |- - |- U U |- U """ backwards_scan = list(scansion.rstrip()) feet = [] candidates = [ self.constants.STRESSED + self.constants.OPTIONAL_ENDING, self.constants.STRESSED + self.constants.STRESSED, self.constants.STRESSED + self.constants.UNSTRESSED, self.constants.UNSTRESSED + self.constants.STRESSED, ] incomplete_foot = self.constants.UNSTRESSED + self.constants.UNSTRESSED try: while len(backwards_scan) > 0: spaces = [] chunk1 = backwards_scan.pop() while len("".join(chunk1).replace(" ", "")) == 0: if len(backwards_scan) == 0: feet.append(chunk1) return feet[::-1] chunk1 = backwards_scan.pop() + "".join(chunk1) chunk2 = backwards_scan.pop() while chunk2 == " ": spaces.append(chunk2) if len(backwards_scan) == 0: feet.append(chunk2) return feet[::-1] chunk2 = backwards_scan.pop() new_candidate = "".join(chunk2) + "".join(spaces) + "".join(chunk1) if new_candidate.replace(" ", "") in candidates: feet.append(new_candidate) else: if new_candidate.replace(" ", "") == incomplete_foot: spaces2 = [] previous_mark = backwards_scan.pop() while previous_mark == " ": spaces2.append(previous_mark) previous_mark = backwards_scan.pop() if previous_mark == self.constants.STRESSED: new_candidate = ( "".join(previous_mark) + "".join(spaces2) + new_candidate ) feet.append(new_candidate) else: feet.append(new_candidate) # invalid foot spaces3 = [] next_mark = backwards_scan.pop() while next_mark == " ": spaces3.append(previous_mark) next_mark = backwards_scan.pop() feet.append( "".join(next_mark) + "".join(spaces3) + previous_mark ) except Exception as ex: LOG.error("err at: {}, {}".format(scansion, ex)) return list() return feet[::-1]
[docs] @staticmethod def hexameter_known_stresses() -> List[int]: """Provide a list of known stress positions for a hexameter. :return: a zero based list enumerating which syllables are known to be stressed. """ return list(range(17)[::3])
[docs] @staticmethod def hexameter_possible_unstresses() -> List[int]: """ Provide a list of possible positions which may be unstressed syllables in a hexameter. :return: a zero based list enumerating which syllables are known to be unstressed. """ return list(set(range(17)) - set(range(17)[::3]))
[docs] def closest_hexameter_patterns(self, scansion: str) -> List[str]: """ Find the closest group of matching valid hexameter patterns. :return: list of the closest valid hexameter patterns; only candidates with a matching length/number of syllables are considered. >>> print(MetricalValidator().closest_hexameter_patterns('-UUUUU-----UU--')) ['-UU-UU-----UU--'] """ return self._closest_patterns(self.VALID_HEXAMETERS, scansion)
[docs] @staticmethod def pentameter_possible_stresses() -> List[int]: """ Provide a list of possible stress positions for a hexameter. :return: a zero based list enumerating which syllables are known to be stressed. """ return list(range(0, 6)) + [8]
[docs] def closest_pentameter_patterns(self, scansion: str) -> List[str]: """ Find the closest group of matching valid pentameter patterns. :return: list of the closest valid pentameter patterns; only candidates with a matching length/number of syllables are considered. >>> print(MetricalValidator().closest_pentameter_patterns('--UUU--UU-UUX')) ['---UU--UU-UUX'] """ return self._closest_patterns(self.VALID_PENTAMETERS, scansion)
[docs] def closest_hendecasyllable_patterns(self, scansion: str) -> List[str]: """ Find the closest group of matching valid hendecasyllable patterns. :return: list of the closest valid hendecasyllable patterns; only candidates with a matching length/number of syllables are considered. >>> print(MetricalValidator().closest_hendecasyllable_patterns('UU-UU-U-U-X')) ['-U-UU-U-U-X', 'U--UU-U-U-X'] """ return self._closest_patterns(self.VALID_HENDECASYLLABLES, scansion)
[docs] def _closest_patterns(self, patterns: List[str], scansion: str) -> List[str]: """ Find the closest group of matching valid patterns. :patterns: a list of patterns :scansion: the scansion pattern thus far :return: list of the closest valid patterns; only candidates with a matching length/number of syllables are considered. """ pattern = scansion.replace(" ", "") pattern = pattern.replace(self.constants.FOOT_SEPARATOR, "") ending = pattern[-1] candidate = pattern[: len(pattern) - 1] + self.constants.OPTIONAL_ENDING cans = [ (distance(candidate, x), x) for x in patterns if len(x) == len(candidate) ] if cans: cans = sorted(cans, key=lambda tup: tup[0]) top = cans[0][0] return [can[1][:-1] + ending for can in cans if can[0] == top] return []
[docs] def _build_hexameter_template(self, stress_positions: str) -> str: """ Build a hexameter scansion template from string of 5 binary numbers; NOTE: Traditionally the fifth foot is dactyl and spondee substitution is rare, however since it *is* a possible combination, we include it here. :param stress_positions: 5 binary integers, indicating whether foot is dactyl or spondee :return: a valid hexameter scansion template, a string representing stressed and unstresssed syllables with the optional terminal ending. >>> print(MetricalValidator()._build_hexameter_template("01010")) -UU---UU---UU-X """ hexameter = [] for binary in stress_positions: if binary == "1": hexameter.append(self.constants.SPONDEE) if binary == "0": hexameter.append(self.constants.DACTYL) hexameter.append(self.constants.HEXAMETER_ENDING) return "".join(hexameter)
def _build_hendecasyllable_templates(self) -> List[str]: return [ # -U - U U - U - U - X self.constants.TROCHEE + self.constants.TROCHEE + self.constants.IAMB + self.constants.IAMB + self.constants.IAMB + self.constants.OPTIONAL_ENDING, # -- - U U - U - U - X self.constants.SPONDEE + self.constants.TROCHEE + self.constants.IAMB + self.constants.IAMB + self.constants.IAMB + self.constants.OPTIONAL_ENDING, # U- - U U - U - U - X self.constants.IAMB + self.constants.TROCHEE + self.constants.IAMB + self.constants.IAMB + self.constants.IAMB + self.constants.OPTIONAL_ENDING, ]
[docs] def _build_pentameter_templates(self) -> List[str]: """Create pentameter templates.""" return [ # '-UU|-UU|-|-UU|-UU|X' self.constants.DACTYL + self.constants.DACTYL + self.constants.STRESSED + self.constants.DACTYL + self.constants.DACTYL + self.constants.OPTIONAL_ENDING, # '-UU|--|-|-UU|-UU|X' self.constants.DACTYL + self.constants.SPONDEE + self.constants.STRESSED + self.constants.DACTYL + self.constants.DACTYL + self.constants.OPTIONAL_ENDING, # '--|-UU|-|-UU|-UU|X' self.constants.SPONDEE + self.constants.DACTYL + self.constants.STRESSED + self.constants.DACTYL + self.constants.DACTYL + self.constants.OPTIONAL_ENDING, # '--|--|-|-UU|-UU|X' self.constants.SPONDEE + self.constants.SPONDEE + self.constants.STRESSED + self.constants.DACTYL + self.constants.DACTYL + self.constants.OPTIONAL_ENDING, ]