def demo():
"""
A demonstration showing how PCFG C{Grammar}s can be created and used.
"""
from en.parser.nltk_lite.corpora import treebank, extract
from en.parser.nltk_lite.parse import cfg, pcfg, pchart, treetransforms
from itertools import islice
# Create some probabilistic CFG Productions
S, A, B, C = cfg.nonterminals('S A B C')
pcfg_prods = [
pcfg.Production(A, [B, B], prob=0.3),
pcfg.Production(A, [C, B, C], prob=0.7),
pcfg.Production(B, [B, 'b'], prob=0.5),
pcfg.Production(B, [C], prob=0.5),
pcfg.Production(C, ['a'], prob=0.1),
pcfg.Production(C, ['b'], prob=0.9)
]
pcfg_prod = pcfg_prods[2]
print 'A PCFG production:', ` pcfg_prod `
print ' pcfg_prod.lhs() =>', ` pcfg_prod.lhs() `
print ' pcfg_prod.rhs() =>', ` pcfg_prod.rhs() `
print ' pcfg_prod.prob() =>', ` pcfg_prod.prob() `
print
# Create and print a PCFG
grammar = pcfg.Grammar(S, pcfg_prods)
print 'A PCFG grammar:', ` grammar `
print ' grammar.start() =>', ` grammar.start() `
print ' grammar.productions() =>',
# Use string.replace(...) is to line-wrap the output.
print ` grammar.productions() `.replace(',', ',\n' + ' ' * 26)
print
# extract productions from three trees and induce the PCFG
print "Induce PCFG grammar from treebank data:"
productions = []
for tree in islice(treebank.parsed(), 3):
# perform optional in-place tree transformations, e.g.:
# treetransforms.collapseUnary(tree, collapsePOS = False)
# treetransforms.chomskyNormalForm(tree, horzMarkov = 2)
productions += tree.productions()
grammar = pcfg.induce(S, productions)
print grammar
print
print "Parse sentence using induced grammar:"
parser = pchart.InsideParse(grammar)
parser.trace(3)
sent = extract(0, treebank.raw())
print sent
for parse in parser.get_parse_list(sent):
print parse
def demo():
from en.parser.nltk_lite.corpora import ieer
from itertools import islice
from pprint import pprint
# pprint(extract(75, ieer.raw()))
pprint(extract(75, ieer.dictionary()))
def demo():
"""
A demonstration showing how PCFG C{Grammar}s can be created and used.
"""
from en.parser.nltk_lite.corpora import treebank, extract
from en.parser.nltk_lite.parse import cfg, pcfg, pchart, treetransforms
from itertools import islice
# Create some probabilistic CFG Productions
S, A, B, C = cfg.nonterminals("S A B C")
pcfg_prods = [
pcfg.Production(A, [B, B], prob=0.3),
pcfg.Production(A, [C, B, C], prob=0.7),
pcfg.Production(B, [B, "b"], prob=0.5),
pcfg.Production(B, [C], prob=0.5),
pcfg.Production(C, ["a"], prob=0.1),
pcfg.Production(C, ["b"], prob=0.9),
]
pcfg_prod = pcfg_prods[2]
print "A PCFG production:", ` pcfg_prod `
print " pcfg_prod.lhs() =>", ` pcfg_prod.lhs() `
print " pcfg_prod.rhs() =>", ` pcfg_prod.rhs() `
print " pcfg_prod.prob() =>", ` pcfg_prod.prob() `
print
# Create and print a PCFG
grammar = pcfg.Grammar(S, pcfg_prods)
print "A PCFG grammar:", ` grammar `
print " grammar.start() =>", ` grammar.start() `
print " grammar.productions() =>",
# Use string.replace(...) is to line-wrap the output.
print ` grammar.productions() `.replace(",", ",\n" + " " * 26)
print
# extract productions from three trees and induce the PCFG
print "Induce PCFG grammar from treebank data:"
productions = []
for tree in islice(treebank.parsed(), 3):
# perform optional in-place tree transformations, e.g.:
# treetransforms.collapseUnary(tree, collapsePOS = False)
# treetransforms.chomskyNormalForm(tree, horzMarkov = 2)
productions += tree.productions()
grammar = pcfg.induce(S, productions)
print grammar
print
print "Parse sentence using induced grammar:"
parser = pchart.InsideParse(grammar)
parser.trace(3)
sent = extract(0, treebank.raw())
print sent
for parse in parser.get_parse_list(sent):
print parse
def demo():
from en.parser.nltk_lite.corpora import ieer
from itertools import islice
from pprint import pprint
# pprint(extract(75, ieer.raw()))
pprint(extract(75, ieer.dictionary()))
