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| # Natural Language Toolkit: Minimal Sets | |
| # | |
| # Copyright (C) 2001-2023 NLTK Project | |
| # Author: Steven Bird <[email protected]> | |
| # URL: <https://www.nltk.org/> | |
| # For license information, see LICENSE.TXT | |
| from collections import defaultdict | |
| class MinimalSet: | |
| """ | |
| Find contexts where more than one possible target value can | |
| appear. E.g. if targets are word-initial letters, and contexts | |
| are the remainders of words, then we would like to find cases like | |
| "fat" vs "cat", and "training" vs "draining". If targets are | |
| parts-of-speech and contexts are words, then we would like to find | |
| cases like wind (noun) 'air in rapid motion', vs wind (verb) | |
| 'coil, wrap'. | |
| """ | |
| def __init__(self, parameters=None): | |
| """ | |
| Create a new minimal set. | |
| :param parameters: The (context, target, display) tuples for the item | |
| :type parameters: list(tuple(str, str, str)) | |
| """ | |
| self._targets = set() # the contrastive information | |
| self._contexts = set() # what we are controlling for | |
| self._seen = defaultdict(set) # to record what we have seen | |
| self._displays = {} # what we will display | |
| if parameters: | |
| for context, target, display in parameters: | |
| self.add(context, target, display) | |
| def add(self, context, target, display): | |
| """ | |
| Add a new item to the minimal set, having the specified | |
| context, target, and display form. | |
| :param context: The context in which the item of interest appears | |
| :type context: str | |
| :param target: The item of interest | |
| :type target: str | |
| :param display: The information to be reported for each item | |
| :type display: str | |
| """ | |
| # Store the set of targets that occurred in this context | |
| self._seen[context].add(target) | |
| # Keep track of which contexts and targets we have seen | |
| self._contexts.add(context) | |
| self._targets.add(target) | |
| # For a given context and target, store the display form | |
| self._displays[(context, target)] = display | |
| def contexts(self, minimum=2): | |
| """ | |
| Determine which contexts occurred with enough distinct targets. | |
| :param minimum: the minimum number of distinct target forms | |
| :type minimum: int | |
| :rtype: list | |
| """ | |
| return [c for c in self._contexts if len(self._seen[c]) >= minimum] | |
| def display(self, context, target, default=""): | |
| if (context, target) in self._displays: | |
| return self._displays[(context, target)] | |
| else: | |
| return default | |
| def display_all(self, context): | |
| result = [] | |
| for target in self._targets: | |
| x = self.display(context, target) | |
| if x: | |
| result.append(x) | |
| return result | |
| def targets(self): | |
| return self._targets | |