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