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February 1, 2018 09:39
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Return all possible ways to cut(tokenize) Thai text.
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import re | |
from collections import defaultdict | |
from marisa_trie import Trie | |
wordlist = [li.strip() for li in open('wordlist.txt')] | |
trie = Trie(wordlist) # สร้างครั้งเดียว ข้างนอก function | |
class LatticeString(str): | |
''' String subclass เพื่อเก็บวิธีตัดหลายๆ วิธี | |
''' | |
def __new__(cls, value, multi=None, in_dict=True): | |
return str.__new__(cls, value) | |
def __init__(self, value, multi=None, in_dict=True): | |
self.unique = True | |
if multi: | |
self.multi = list(multi) | |
if len(self.multi) > 1: | |
self.unique = False | |
else: | |
self.multi = [value] | |
self.in_dict = in_dict # บอกว่าเป็นคำมีในดิกหรือเปล่า | |
pat_eng = re.compile(r'''(?x) | |
[-a-zA-Z]+| # english | |
\d[\d,\.]*| # number | |
[ \t]+| # space | |
\r?\n # newline | |
''') | |
def multicut(text): | |
''' ส่งคืน LatticeString คืนมาเป็นก้อนๆ | |
''' | |
words_at = defaultdict(list) # main data structure | |
def serialize(p, p2): # helper function | |
for w in words_at[p]: | |
p_ = p + len(w) | |
if p_== p2: | |
yield w | |
elif p_ < p2: | |
for path in serialize(p_, p2): | |
yield w+'/'+path | |
q = {0} | |
last_p = 0 # last position for yield | |
while min(q) < len(text): | |
p = min(q) | |
q -= {p} # q.pop, but for set | |
for w in trie.prefixes(text[p:]): | |
words_at[p].append(w) | |
q.add(p+len(w)) | |
if len(q)==1: | |
q0 = min(q) | |
yield LatticeString(text[last_p:q0], serialize(last_p, q0)) | |
last_p = q0 | |
# กรณี len(q) == 0 คือ ไม่มีใน dict | |
if len(q)==0: | |
m = pat_eng.match(text[p:]) | |
if m: # อังกฤษ, เลข, ว่าง | |
i = p + m.span()[1] | |
else: # skip น้อยที่สุด ที่เป็นไปได้ | |
for i in range(p, len(text)): | |
ww = trie.prefixes(text[i:]) | |
m = pat_eng.match(text[i:]) | |
if ww or m: | |
break | |
else: | |
i = len(text) | |
w = text[p:i] | |
words_at[p].append(w) | |
yield LatticeString(w, in_dict=False) | |
last_p = i | |
q.add(i) | |
def mmcut(text): | |
''' Maximal Matching algorithm ในการตัดคำภาษาไทย | |
''' | |
res = [] | |
for w in multicut(text): | |
mm = min(w.multi, key=lambda x: x.count('/')) | |
res.extend(mm.split('/')) | |
return res |
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เขียนใหม่ ทำ maximal matching อย่างเดียว จะได้เร็วขึ้น ไม่ต้องเสียเวลาสร้าง LatticeString
https://colab.research.google.com/notebook#fileId=1V1Z657_5eSWPo8rLfVRwA0A5E4vkg7SI