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wordseg.py
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wordseg.py
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#-*- coding:utf-8 -*-
"""
Chinese word segmentation algorithm with corpus
Author: "Xylander"
"""
import os
import re
import math
import time
from entropy import compute_entropy
from extract import extract_cadicateword,gen_bigram
import pandas as pd
import codecs
class wordinfo(object):
'''
Record every candidate word information include left neighbors, right neighbors, frequency, PMI
'''
def __init__(self,text):
super(wordinfo,self).__init__()
self.text = text
self.freq = 0.0
self.left = [] #record left neighbors
self.right = [] #record right neighbors
self.pmi = 0
def update_data(self,left,right):
self.freq += 1.0
if left:
self.left.append(left)
if right:
self.right.append(right)
def compute_indexes(self,length):
#compute frequency of word,and left/right entropy
self.freq /= length
self.left = compute_entropy(self.left)
self.right = compute_entropy(self.right)
def compute_pmi(self,words_dict):
#compute all kinds of combines for word
sub_part = gen_bigram(self.text)
if len(sub_part) > 0:
self.pmi = min(map(lambda word : math.log(self.freq/words_dict[word[0]].freq/words_dict[word[1]].freq),sub_part))
class segdocument(object):
'''
Main class for Chinese word segmentation
1. Generate words from a long enough document
2. Do the segmentation work with the document
reference:
'''
def __init__(self,doc,max_word_len=5,min_tf=0.000005,min_entropy=0.07,min_pmi=6.0):
super(segdocument,self).__init__()
self.max_word_len = max_word_len
self.min_tf = min_tf
self.min_entropy = min_entropy
self.min_pmi = min_pmi
#analysis documents
self.word_info = self.gen_words(doc)
count = float(len(self.word_info))
self.avg_frq = sum(map(lambda w : w.freq,self.word_info))/count
self.avg_entropy = sum(map(lambda w : min(w.left,w.right),self.word_info))/count
self.avg_pmi = sum(map(lambda w:w.pmi,self.word_info)) / count
filter_function = lambda f:len(f.text) > 1 and f.pmi > self.min_pmi and f.freq > self.min_tf\
and min(f.left,f.right) > self.min_entropy
self.word_tf_pmi_ent = map(lambda w :(w.text,len(w.text),w.freq,w.pmi,min(w.left,w.right)),filter(filter_function,self.word_info))
def gen_words(self,doc):
#pattern = re.compile('[:“。”,!?、《》……;’‘\n——\r\t)、(——^[1-9]d*$]')
#pattern = re.compile('[\s+\.\!\/_,$%^*(+\"\']+|[+——!,。??:、~@#”“¥:%……&*()]+|[[A-Za-z0-9]*$]'.decode('utf-8'))
pattern = re.compile(u'[\\s\\d,.<>/?:;\'\"[\\]{}()\\|~!@#$%^&*\\-_=+a-zA-Z,。《》、?:;“”‘’{}【】()…¥!—┄-]+')
doc = pattern.sub(r'',doc)
word_index = extract_cadicateword(doc,self.max_word_len)
word_cad = {} #后选词的字典
for suffix in word_index:
word = doc[suffix[0]:suffix[1]]
if word not in word_cad:
word_cad[word] = wordinfo(word)
# record frequency of word and left neighbors and right neighbors
word_cad[word].update_data(doc[suffix[0]-1:suffix[0]],doc[suffix[1]:suffix[1]+1])
length = len(doc)
#computing frequency of candicate word and entropy of left/right neighbors
for word in word_cad:
word_cad[word].compute_indexes(length)
#ranking by length of word
values = sorted(word_cad.values(),key=lambda x:len(x.text))
for v in values:
if len(v.text) == 1:
continue
v.compute_pmi(word_cad)
# ranking by freq
return sorted(values,key = lambda v: len(v.text),reverse = False)
if __name__ == '__main__':
starttime = time.clock()
path = os.path.abspath('.')
wordlist = []
word_candidate = []
dict_bank = []
dict_path = path + '\\dict.txt'
doc = codecs.open(path+'\\train_for_ws.txt', "r", "utf-8").read()
word = segdocument(doc,max_word_len=3,min_tf=(1e-08),min_entropy=1.0,min_pmi=3.0)
print('avg_frq:'+ str(word.avg_frq))
print('avg_pmi:' + str(word.avg_pmi))
print('avg_entropy:'+ str(word.avg_entropy))
for i in codecs.open(dict_path, 'r', "utf-8"):
dict_bank.append(i.split(' ')[0])
print('result:')
for i in word.word_tf_pmi_ent:
if i[0] not in dict_bank:
word_candidate.append(i[0])
wordlist.append([i[0],i[1],i[2],i[3],i[4]])
# ranking on entropy (primary key) and pmi (secondary key)
wordlist = sorted(wordlist, key=lambda word: word[3], reverse=True)
wordlist = sorted(wordlist, key=lambda word: word[4], reverse=True)
seg = pd.DataFrame(wordlist,columns=['word','length','fre','pmi','entropy'])
seg.to_csv(path+'/extractword.csv', index=False ,encoding="utf-8")
# intersection = set(word_candidate) & set(dict_bank)
# newwordset = set(word_candidate) - intersection
# for i in wordlist:
# print(i[0],i[1],i[2],i[3],i[4])
endtime = time.clock()
print(endtime-starttime)