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125 lines
4.4 KiB
ReStructuredText
125 lines
4.4 KiB
ReStructuredText
================
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The Token Object
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================
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A Token represents a single word, punctuation or significant whitespace symbol.
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Integer IDs are provided for all string features. The (unicode) string is
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provided by an attribute of the same name followed by an underscore, e.g.
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token.orth is an integer ID, token.orth\_ is the unicode value.
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The only exception is the Token.string attribute, which is (unicode)
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string-typed.
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**String Features**
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:code:`string`
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The form of the word as it appears in the string, include trailing
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whitespace. This is useful when you need to use linguistic features to
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add inline mark-up to the string.
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:code:`orth` / :code:`orth_`
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The form of the word with no string normalization or processing, as it
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appears in the string, without trailing whitespace.
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:code:`lemma` / :code:`lemma_`
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The "base" of the word, with no inflectional suffixes, e.g. the lemma of
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"developing" is "develop", the lemma of "geese" is "goose", etc. Note that
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*derivational* suffixes are not stripped, e.g. the lemma of "instutitions"
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is "institution", not "institute". Lemmatization is performed using the
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WordNet data, but extended to also cover closed-class words such as
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pronouns. By default, the WN lemmatizer returns "hi" as the lemma of "his".
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We assign pronouns the lemma -PRON-.
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:code:`lower` / :code:`lower_`
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The form of the word, but forced to lower-case, i.e. lower = word.orth\_.lower()
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:code:`norm` / :code:`norm_`
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The form of the word, after language-specific normalizations have been
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applied.
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:code:`shape` / :code:`shape_`
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A transform of the word's string, to show orthographic features. The
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characters a-z are mapped to x, A-Z is mapped to X, 0-9 is mapped to d.
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After these mappings, sequences of 4 or more of the same character are
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truncated to length 4. Examples: C3Po --> XdXx, favorite --> xxxx,
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:) --> :)
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:code:`prefix` / :code:`prefix_`
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A length-N substring from the start of the word. Length may vary by
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language; currently for English n=1, i.e. prefix = word.orth\_[:1]
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:code:`suffix` / :code:`suffix_`
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A length-N substring from the end of the word. Length may vary by
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language; currently for English n=3, i.e. suffix = word.orth\_[-3:]
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**Distributional Features**
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:code:`prob`
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The unigram log-probability of the word, estimated from counts from a
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large corpus, smoothed using Simple Good Turing estimation.
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:code:`cluster`
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The Brown cluster ID of the word. These are often useful features for
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linear models. If you're using a non-linear model, particularly
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a neural net or random forest, consider using the real-valued word
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representation vector, in Token.repvec, instead.
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:code:`repvec`
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A "word embedding" representation: a dense real-valued vector that supports
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similarity queries between words. By default, spaCy currently loads
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vectors produced by the Levy and Goldberg (2014) dependency-based word2vec
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model.
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**Syntactic Features**
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:code:`tag`
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A morphosyntactic tag, e.g. NN, VBZ, DT, etc. These tags are
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language/corpus specific, and typically describe part-of-speech and some
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amount of morphological information. For instance, in the Penn Treebank
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tag set, VBZ is assigned to a present-tense singular verb.
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:code:`pos`
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A part-of-speech tag, from the Google Universal Tag Set, e.g. NOUN, VERB,
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ADV. Constants for the 17 tag values are provided in spacy.parts\_of\_speech.
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:code:`dep`
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The type of syntactic dependency relation between the word and its
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syntactic head.
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:code:`n_lefts`
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The number of immediate syntactic children preceding the word in the
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string.
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:code:`n_rights`
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The number of immediate syntactic children following the word in the
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string.
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**Navigating the Dependency Tree**
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:code:`head`
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The Token that is the immediate syntactic head of the word. If the word is
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the root of the dependency tree, the same word is returned.
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:code:`lefts`
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An iterator for the immediate leftward syntactic children of the word.
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:code:`rights`
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An iterator for the immediate rightward syntactic children of the word.
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:code:`children`
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An iterator that yields from lefts, and then yields from rights.
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:code:`subtree`
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An iterator for the part of the sentence syntactically governed by the
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word, including the word itself.
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**Named Entities**
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:code:`ent_type`
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If the token is part of an entity, its entity type
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:code:`ent_iob`
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The IOB (inside, outside, begin) entity recognition tag for the token
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