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| """Library containing Tokenizer definitions. |
| |
| The RougeScorer class can be instantiated with the tokenizers defined here. New |
| tokenizers can be defined by creating a subclass of the Tokenizer abstract class |
| and overriding the tokenize() method. |
| """ |
| import abc |
| from nltk.stem import porter |
| from rouge import tokenize |
|
|
|
|
| class Tokenizer(abc.ABC): |
| """Abstract base class for a tokenizer. |
| |
| Subclasses of Tokenizer must implement the tokenize() method. |
| """ |
|
|
| @abc.abstractmethod |
| def tokenize(self, text): |
| raise NotImplementedError("Tokenizer must override tokenize() method") |
|
|
|
|
| class DefaultTokenizer(Tokenizer): |
| """Default tokenizer which tokenizes on whitespace.""" |
|
|
| def __init__(self, use_stemmer=False): |
| """Constructor for DefaultTokenizer. |
| |
| Args: |
| use_stemmer: boolean, indicating whether Porter stemmer should be used to |
| strip word suffixes to improve matching. |
| """ |
| self._stemmer = porter.PorterStemmer() if use_stemmer else None |
|
|
| def tokenize(self, text): |
| return tokenize.tokenize(text, self._stemmer) |
|
|
