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238 lines
11 KiB
Plaintext
238 lines
11 KiB
Plaintext
//- 💫 DOCS > USAGE > LINGUISTIC FEATURES > DEPENDENCY PARSE
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p
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| spaCy features a fast and accurate syntactic dependency parser, and has
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| a rich API for navigating the tree. The parser also powers the sentence
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| boundary detection, and lets you iterate over base noun phrases, or
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| "chunks". You can check whether a #[+api("doc") #[code Doc]] object has
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| been parsed with the #[code doc.is_parsed] attribute, which returns a
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| boolean value. If this attribute is #[code False], the default sentence
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| iterator will raise an exception.
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+h(3, "noun-chunks") Noun chunks
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p
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| Noun chunks are "base noun phrases" – flat phrases that have a noun as
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| their head. You can think of noun chunks as a noun plus the words describing
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| the noun – for example, "the lavish green grass" or "the world’s largest
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| tech fund". To get the noun chunks in a document, simply iterate over
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| #[+api("doc#noun_chunks") #[code Doc.noun_chunks]].
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+code("Example").
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nlp = spacy.load('en')
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doc = nlp(u'Autonomous cars shift insurance liability toward manufacturers')
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for chunk in doc.noun_chunks:
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print(chunk.text, chunk.root.text, chunk.root.dep_,
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chunk.root.head.text)
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+aside
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| #[strong Text:] The original noun chunk text.#[br]
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| #[strong Root text:] The original text of the word connecting the noun
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| chunk to the rest of the parse.#[br]
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| #[strong Root dep:] Dependcy relation connecting the root to its head.#[br]
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| #[strong Root head text:] The text of the root token's head.#[br]
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+table(["Text", "root.text", "root.dep_", "root.head.text"])
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- var style = [0, 0, 1, 0]
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+annotation-row(["Autonomous cars", "cars", "nsubj", "shift"], style)
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+annotation-row(["insurance liability", "liability", "dobj", "shift"], style)
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+annotation-row(["manufacturers", "manufacturers", "pobj", "toward"], style)
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+h(3, "navigating") Navigating the parse tree
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p
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| spaCy uses the terms #[strong head] and #[strong child] to describe the words
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| #[strong connected by a single arc] in the dependency tree. The term
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| #[strong dep] is used for the arc label, which describes the type of
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| syntactic relation that connects the child to the head. As with other
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| attributes, the value of #[code .dep] is a hash value. You can get
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| the string value with #[code .dep_].
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+code("Example").
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doc = nlp(u'Autonomous cars shift insurance liability toward manufacturers')
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for token in doc:
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print(token.text, token.dep_, token.head.text, token.head.pos_,
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[child for child in token.children])
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+aside
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| #[strong Text]: The original token text.#[br]
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| #[strong Dep]: The syntactic relation connecting child to head.#[br]
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| #[strong Head text]: The original text of the token head.#[br]
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| #[strong Head POS]: The part-of-speech tag of the token head.#[br]
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| #[strong Children]: The immediate syntactic dependents of the token.
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+table(["Text", "Dep", "Head text", "Head POS", "Children"])
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- var style = [0, 1, 0, 1, 0]
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+annotation-row(["Autonomous", "amod", "cars", "NOUN", ""], style)
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+annotation-row(["cars", "nsubj", "shift", "VERB", "Autonomous"], style)
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+annotation-row(["shift", "ROOT", "shift", "VERB", "cars, liability"], style)
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+annotation-row(["insurance", "compound", "liability", "NOUN", ""], style)
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+annotation-row(["liability", "dobj", "shift", "VERB", "insurance, toward"], style)
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+annotation-row(["toward", "prep", "liability", "NOUN", "manufacturers"], style)
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+annotation-row(["manufacturers", "pobj", "toward", "ADP", ""], style)
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+codepen("dcf8d293367ca185b935ed2ca11ebedd", 370)
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p
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| Because the syntactic relations form a tree, every word has
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| #[strong exactly one head]. You can therefore iterate over the arcs in
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| the tree by iterating over the words in the sentence. This is usually
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| the best way to match an arc of interest — from below:
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+code.
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from spacy.symbols import nsubj, VERB
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# Finding a verb with a subject from below — good
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verbs = set()
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for possible_subject in doc:
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if possible_subject.dep == nsubj and possible_subject.head.pos == VERB:
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verbs.add(possible_subject.head)
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p
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| If you try to match from above, you'll have to iterate twice: once for
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| the head, and then again through the children:
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+code.
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# Finding a verb with a subject from above — less good
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verbs = []
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for possible_verb in doc:
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if possible_verb.pos == VERB:
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for possible_subject in possible_verb.children:
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if possible_subject.dep == nsubj:
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verbs.append(possible_verb)
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break
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p
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| To iterate through the children, use the #[code token.children]
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| attribute, which provides a sequence of #[+api("token") #[code Token]]
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| objects.
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+h(4, "navigating-around") Iterating around the local tree
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p
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| A few more convenience attributes are provided for iterating around the
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| local tree from the token. The #[+api("token#lefts") #[code Token.lefts]]
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| and #[+api("token#rights") #[code Token.rights]] attributes provide
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| sequences of syntactic children that occur before and after the token.
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| Both sequences are in sentence order. There are also two integer-typed
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| attributes, #[+api("token#n_rights") #[code Token.n_rights]] and
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| #[+api("token#n_lefts") #[code Token.n_lefts]], that give the number of
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| left and right children.
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+code.
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doc = nlp(u'bright red apples on the tree')
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assert [token.text for token in doc[2].lefts]) == [u'bright', u'red']
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assert [token.text for token in doc[2].rights]) == ['on']
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assert doc[2].n_lefts == 2
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assert doc[2].n_rights == 1
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p
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| You can get a whole phrase by its syntactic head using the
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| #[+api("token#subtree") #[code Token.subtree]] attribute. This returns an
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| ordered sequence of tokens. You can walk up the tree with the
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| #[+api("token#ancestors") #[code Token.ancestors]] attribute, and
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| check dominance with
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| #[+api("token#is_ancestor") #[code Token.is_ancestor()]].
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+aside("Projective vs. non-projective")
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| For the #[+a("/models/en") default English model], the
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| parse tree is #[strong projective], which means that there are no crossing
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| brackets. The tokens returned by #[code .subtree] are therefore guaranteed
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| to be contiguous. This is not true for the German model, which has many
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| #[+a(COMPANY_URL + "/blog/german-model#word-order", true) non-projective dependencies].
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+code.
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doc = nlp(u'Credit and mortgage account holders must submit their requests')
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root = [token for token in doc if token.head is token][0]
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subject = list(root.lefts)[0]
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for descendant in subject.subtree:
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assert subject.is_ancestor(descendant)
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print(descendant.text, descendant.dep_, descendant.n_lefts, descendant.n_rights,
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[ancestor.text for ancestor in descendant.ancestors])
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+table(["Text", "Dep", "n_lefts", "n_rights", "ancestors"])
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- var style = [0, 1, 1, 1, 0]
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+annotation-row(["Credit", "nmod", 0, 2, "holders, submit"], style)
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+annotation-row(["and", "cc", 0, 0, "Credit, holders, submit"], style)
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+annotation-row(["mortgage", "compound", 0, 0, "account, Credit, holders, submit"], style)
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+annotation-row(["account", "conj", 1, 0, "Credit, holders, submit"], style)
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+annotation-row(["holders", "nsubj", 1, 0, "submit"], style)
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p
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| Finally, the #[code .left_edge] and #[code .right_edge] attributes
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| can be especially useful, because they give you the first and last token
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| of the subtree. This is the easiest way to create a #[code Span] object
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| for a syntactic phrase. Note that #[code .right_edge] gives a token
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| #[strong within] the subtree — so if you use it as the end-point of a
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| range, don't forget to #[code +1]!
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+code.
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doc = nlp(u'Credit and mortgage account holders must submit their requests')
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span = doc[doc[4].left_edge.i : doc[4].right_edge.i+1]
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span.merge()
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for token in doc:
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print(token.text, token.pos_, token.dep_, token.head.text)
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+table(["Text", "POS", "Dep", "Head text"])
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- var style = [0, 1, 1, 0]
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+annotation-row(["Credit and mortgage account holders", "NOUN", "nsubj", "submit"], style)
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+annotation-row(["must", "VERB", "aux", "submit"], style)
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+annotation-row(["submit", "VERB", "ROOT", "submit"], style)
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+annotation-row(["their", "ADJ", "poss", "requests"], style)
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+annotation-row(["requests", "NOUN", "dobj", "submit"], style)
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+h(3, "displacy") Visualizing dependencies
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p
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| The best way to understand spaCy's dependency parser is interactively.
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| To make this easier, spaCy v2.0+ comes with a visualization module. Simply
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| pass a #[code Doc] or a list of #[code Doc] objects to
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| displaCy and run #[+api("displacy#serve") #[code displacy.serve]] to
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| run the web server, or #[+api("displacy#render") #[code displacy.render]]
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| to generate the raw markup. If you want to know how to write rules that
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| hook into some type of syntactic construction, just plug the sentence into
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| the visualizer and see how spaCy annotates it.
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+code.
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from spacy import displacy
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doc = nlp(u'Autonomous cars shift insurance liability toward manufacturers')
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displacy.serve(doc, style='dep')
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+infobox
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| For more details and examples, see the
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| #[+a("/usage/visualizers") usage guide on visualizing spaCy]. You
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| can also test displaCy in our #[+a(DEMOS_URL + "/displacy", true) online demo].
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+h(3, "disabling") Disabling the parser
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p
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| In the #[+a("/models") default models], the parser is loaded and enabled
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| as part of the
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| #[+a("docs/usage/language-processing-pipelines") standard processing pipeline].
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| If you don't need any of the syntactic information, you should disable
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| the parser. Disabling the parser will make spaCy load and run much faster.
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| If you want to load the parser, but need to disable it for specific
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| documents, you can also control its use on the #[code nlp] object.
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+code.
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nlp = spacy.load('en', disable=['parser'])
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nlp = English().from_disk('/model', disable=['parser'])
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doc = nlp(u"I don't want parsed", disable=['parser'])
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+infobox("Important note: disabling pipeline components")
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.o-block
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| Since spaCy v2.0 comes with better support for customising the
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| processing pipeline components, the #[code parser] keyword argument
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| has been replaced with #[code disable], which takes a list of
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| #[+a("/usage/processing-pipelines") pipeline component names].
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| This lets you disable both default and custom components when loading
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| a model, or initialising a Language class via
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| #[+api("language-from_disk") #[code from_disk]].
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+code-new.
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nlp = spacy.load('en', disable=['parser'])
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doc = nlp(u"I don't want parsed", disable=['parser'])
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+code-old.
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nlp = spacy.load('en', parser=False)
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doc = nlp(u"I don't want parsed", parse=False)
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