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| """A library for tokenizing text.""" |
|
|
| from __future__ import absolute_import |
| from __future__ import division |
| from __future__ import print_function |
|
|
| import re |
| import six |
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| |
| NON_ALPHANUM_PATTERN = r"[^a-z0-9]+" |
| NON_ALPHANUM_RE = re.compile(NON_ALPHANUM_PATTERN) |
| SPACES_PATTERN = r"\s+" |
| SPACES_RE = re.compile(SPACES_PATTERN) |
| VALID_TOKEN_PATTERN = r"^[a-z0-9]+$" |
| VALID_TOKEN_RE = re.compile(VALID_TOKEN_PATTERN) |
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|
| def tokenize(text, stemmer): |
| """Tokenize input text into a list of tokens. |
| |
| This approach aims to replicate the approach taken by Chin-Yew Lin in |
| the original ROUGE implementation. |
| |
| Args: |
| text: A text blob to tokenize. |
| stemmer: An optional stemmer. |
| |
| Returns: |
| A list of string tokens extracted from input text. |
| """ |
|
|
| |
| text = text.lower() |
| |
| text = NON_ALPHANUM_RE.sub(" ", six.ensure_str(text)) |
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| tokens = SPACES_RE.split(text) |
| if stemmer: |
| |
| tokens = [six.ensure_str(stemmer.stem(x)) if len(x) > 3 else x |
| for x in tokens] |
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| |
| tokens = [x for x in tokens if VALID_TOKEN_RE.match(x)] |
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| return tokens |
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|