簡單語法在Python中給ValueError

我是Python新手，nltk和nlp。我寫了簡單的語法。但是在運行該程序時，會出現以下錯誤。請幫我解決這個錯誤簡單語法在Python中給ValueError

語法： -

S -> NP 
NP -> PN|PRO|D[NUM=?n] N[NUM=?n]|D[NUM=?n] A N[NUM=?n]|D[NUM=?n] N[NUM=?n] PP|QP N[NUM=?n]|A N[NUM=?n]|D[NUM=?n] NOM PP|D[NUM=?n] NOM 
PP -> P NP 
D[NUM=sg] -> 'a' 
D -> 'the' 
N[NUM=sg] -> 'boy'|'girl'|'room'|'garden'|'hair' 
N[NUM=pl] -> 'dogs'|'cats' 
PN -> 'saumya'|'dinesh' 
PRO -> 'she'|'he'|'we' 
A -> 'tall'|'naughty'|'long'|'three'|'black' 
P -> 'with'|'in'|'from'|'at' 
QP -> 'some' 
NOM -> A NOM|N[NUM=?n]

代碼： -

import nltk 

grammar = nltk.data.load('file:english_grammer.cfg') 
rdparser = nltk.RecursiveDescentParser(grammar) 
sent = "a dogs".split() 
trees = rdparser.parse(sent) 

for tree in trees: print (tree)

錯誤： -

來源

2014-10-22 Chandana Indisooriya

請同時發佈代碼中的完整錯誤追溯。 – alvas 2014-10-22 13:54:13

我不認爲NLTK CFG語法讀者可以用方括號讀取CFG的格式。

首先讓我們嘗試CFG語法不加方括號：

from nltk.grammar import CFG 

grammar_string = ''' 
S -> NP 
PP -> P NP 
D -> 'the' 
PN -> 'saumya'|'dinesh' 
PRO -> 'she'|'he'|'we' 
A -> 'tall'|'naughty'|'long'|'three'|'black' 
P -> 'with'|'in'|'from'|'at' 
QP -> 'some' 
''' 

grammar = CFG.fromstring(grammar_string) 
print grammar

[出]：

Grammar with 18 productions (start state = S) 
    S -> NP 
    PP -> P NP 
    D -> 'the' 
    PN -> 'saumya' 
    PN -> 'dinesh' 
    PRO -> 'she' 
    PRO -> 'he' 
    PRO -> 'we' 
    A -> 'tall' 
    A -> 'naughty' 
    A -> 'long' 
    A -> 'three' 
    A -> 'black' 
    P -> 'with' 
    P -> 'in' 
    P -> 'from' 
    P -> 'at' 
    QP -> 'some'

現在，讓我們把方括號：

from nltk.grammar import CFG 

grammar_string = ''' 
S -> NP 
PP -> P NP 
D -> 'the' 
PN -> 'saumya'|'dinesh' 
PRO -> 'she'|'he'|'we' 
A -> 'tall'|'naughty'|'long'|'three'|'black' 
P -> 'with'|'in'|'from'|'at' 
QP -> 'some' 
N[NUM=sg] -> 'boy'|'girl'|'room'|'garden'|'hair' 
N[NUM=pl] -> 'dogs'|'cats' 
''' 

grammar = CFG.fromstring(grammar_string) 
print grammar

[出]：

Traceback (most recent call last): 
    File "test.py", line 33, in <module> 
    grammar = CFG.fromstring(grammar_string) 
    File "/usr/local/lib/python2.7/dist-packages/nltk/grammar.py", line 519, in fromstring 
    encoding=encoding) 
    File "/usr/local/lib/python2.7/dist-packages/nltk/grammar.py", line 1273, in read_grammar 
    (linenum+1, line, e)) 
ValueError: Unable to parse line 10: N[NUM=sg] -> 'boy'|'girl'|'room'|'garden'|'hair' 
Expected an arrow

再回到你的語法，好像你正在使用的方括號表示約束或uncontraints，因此該解決方案將是：

使用強調了contrainted非終端和
做出了unconstrainted非終端

規則，以便您的CFG規則將如下這樣：

from nltk.parse import RecursiveDescentParser 
from nltk.grammar import CFG 

grammar_string = ''' 
S -> NP 
NP -> PN | PRO | D N | D A N | D N PP | QP N | A N | D NOM PP | D NOM 

PP -> P NP 
PN -> 'saumya'|'dinesh' 
PRO -> 'she'|'he'|'we' 
A -> 'tall'|'naughty'|'long'|'three'|'black' 
P -> 'with'|'in'|'from'|'at' 
QP -> 'some' 

D -> D_def | D_sg 
D_def -> 'the' 
D_sg -> 'a' 

N -> N_sg | N_pl 
N_sg -> 'boy'|'girl'|'room'|'garden'|'hair' 
N_pl -> 'dogs'|'cats' 
''' 

grammar = CFG.fromstring(grammar_string) 

rdparser = RecursiveDescentParser(grammar) 
sent = "a dogs".split() 
trees = rdparser.parse(sent) 

for tree in trees: 
    print (tree)

[出]：

(S (NP (D (D_sg a)) (N (N_pl dogs))))

來源

2014-10-22 14:16:33 alvas

感謝您的迴應。其實我想要的是從我的語法中排除以下不合格的句子。（i）。狗（ii）。三個女孩（iii）。他的貓 – 2014-10-22 17:35:29

該帖子解決了您發佈的錯誤。所以我想剩下的就是你的家庭作業了，你可以做到這一點，牢記在非終端中不允許使用括號，並且在NLTK API的cfg中沒有限制。玩的開心！ – alvas 2014-10-22 19:33:18

感謝您的更新。我會試一試.. – 2014-10-23 10:55:19

它看起來就像你試圖用NLTK的功能語法，這確實使用了方括號的語法來表示的特性和功能的協議。 NLTK使用特徵語法的解析器是FeatureEarleyChartParser（與RecursiveDescentParser相反）。

從NLTK documentation：

>>> from __future__ import print_function 
>>> import nltk 
>>> from nltk import grammar, parse 
>>> g = """ 
... % start DP 
... DP[AGR=?a] -> D[AGR=?a] N[AGR=?a] 
... D[AGR=[NUM='sg', PERS=3]] -> 'this' | 'that' 
... D[AGR=[NUM='pl', PERS=3]] -> 'these' | 'those' 
... D[AGR=[NUM='pl', PERS=1]] -> 'we' 
... D[AGR=[PERS=2]] -> 'you' 
... N[AGR=[NUM='sg', GND='m']] -> 'boy' 
... N[AGR=[NUM='pl', GND='m']] -> 'boys' 
... N[AGR=[NUM='sg', GND='f']] -> 'girl' 
... N[AGR=[NUM='pl', GND='f']] -> 'girls' 
... N[AGR=[NUM='sg']] -> 'student' 
... N[AGR=[NUM='pl']] -> 'students' 
... """ 
>>> grammar = grammar.FeatureGrammar.fromstring(g) 
>>> tokens = 'these girls'.split() 
>>> parser = parse.FeatureEarleyChartParser(grammar) 
>>> trees = parser.parse(tokens) 
>>> for tree in trees: print(tree) 
(DP[AGR=[GND='f', NUM='pl', PERS=3]] 
    (D[AGR=[NUM='pl', PERS=3]] these) 
    (N[AGR=[GND='f', NUM='pl']] girls))

來源

2015-02-25 00:43:58 dantiston

感謝您的建議。我設法通過將grammar = nltk.data.load（'file：english_grammer.cfg'）更改爲grammar = nltk.data.load（'file：english_grammer.fcfg'）來解決此問題。 – 2015-03-03 09:33:05

店在NLTK包.fcfg推廣和使用load_parser語法。

例如：english_grammer。 fcfg

我用下面的代碼加載它。

import nltk 
from nltk import load_parser 
chart = load_parser('file:english_grammer.fcfg') 
sent = 'the girl gave the dog a bone'.split() 
trees = chart.nbest_parse(sent) 
for tree in trees: print tree

這就解決了我的問題。

來源

2017-01-19 19:27:33

簡單語法在Python中給ValueError

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