創(chuàng)建句子
上節(jié)是拆分句子片仿，這節(jié)要將拆出的詞匯再次組成句子。
一個簡單句子是由
主語(subject)+謂語(動詞 verb)+賓語(object)
構(gòu)成的
class ParseError(Exception):
pass
class Sentence(object):
def __init__(self, subject, verb, object):
self.subject = subject[1]
self.verb = verb[1]
self.object = object[1]
def peek(word_list):
if word_list:
word = word_list[0]
return word[0]
else:
return None
def match(word_list,expecting):
if word_list:
word = word_list.pop(0)
if word[0] == expecting:
return word
else:
return None
else:
return None
def skip(word_list,word_type):
while peek(word_list) == word_type:
match(word_list,word_type)
def parse_verb(word_list):
skip(word_list,'stop')
if peek(word_list) == 'verb':
return match(word_list,'verb')
else:
raise ParseError("Excepted a verb next.")
def parse_object(word_list):
skip(word_list,'stop')
next = peek(word_list)
if next == 'noun':
return match(word_list,'noun')
if next == 'direction':
return match(word_list,'direction')
else:
raise ParseError("Excepted a noun or direction next.")
def parse_subject(word_list,subj):
verb = parse_verb(word_list)
obj = parse_object(word_list)
return Sentence(subj,verb,obj)
def parse_sentence(word_list):
skip(word_list,'stop')
start = peek(word_list)
if start == 'noun':
subj = match(word_list,'noun')
return parse_subject(word_list,subj)
elif start == 'verb':
return parse_subject(word_list,('noun','player'))
else:
raise ParseError("must start with subject, object, or verb not : %s" % start)
