Python 敏感词过滤的实现示例

class NaiveFilter():
 '''Filter Messages from keywords
 very simple filter implementation
 >>> f = NaiveFilter()
 >>> f.parse("filepath")
 >>> f.filter("hello sexy baby")
 hello **** baby
 '''
 def __init__(self):
  self.keywords = set([])
 def parse(self, path):
  for keyword in open(path):
self.keywords.add(keyword.strip().decode('utf-8').lower())
 def filter(self, message, repl="*"):
  message = str(message).lower()
  for kw in self.keywords:
message = message.replace(kw, repl)
  return message

class BSFilter:
 '''Filter Messages from keywords
 Use Back Sorted Mapping to reduce replacement times
 >>> f = BSFilter()
 >>> f.add("sexy")
 >>> f.filter("hello sexy baby")
 hello **** baby
 '''
 def __init__(self):
  self.keywords = []
  self.kwsets = set([])
  self.bsdict = defaultdict(set)
  self.pat_en = re.compile(r'^[0-9a-zA-Z]+$')  # english phrase or not
 def add(self, keyword):
  if not isinstance(keyword, str):
keyword = keyword.decode('utf-8')
  keyword = keyword.lower()
  if keyword not in self.kwsets:
self.keywords.append(keyword)
self.kwsets.add(keyword)
index = len(self.keywords) - 1
for word in keyword.split():
 if self.pat_en.search(word):
  self.bsdict[word].add(index)
 else:
  for char in word:self.bsdict[char].add(index)
 def parse(self, path):
  with open(path, "r") as f:
for keyword in f:
 self.add(keyword.strip())
 def filter(self, message, repl="*"):
  if not isinstance(message, str):
message = message.decode('utf-8')
  message = message.lower()
  for word in message.split():
if self.pat_en.search(word):
 for index in self.bsdict[word]:
  message = message.replace(self.keywords[index], repl)
else:
 for char in word:
  for index in self.bsdict[char]:message = message.replace(self.keywords[index], repl)
  return message

class DFAFilter():
 '''Filter Messages from keywords
 Use DFA to keep algorithm perform constantly
 >>> f = DFAFilter()
 >>> f.add("sexy")
 >>> f.filter("hello sexy baby")
 hello **** baby
 '''
 def __init__(self):
  self.keyword_chains = {}
  self.delimit = '\x00'
 def add(self, keyword):
  if not isinstance(keyword, str):
keyword = keyword.decode('utf-8')
  keyword = keyword.lower()
  chars = keyword.strip()
  if not chars:
return
  level = self.keyword_chains
  for i in range(len(chars)):
if chars[i] in level:
 level = level[chars[i]]
else:
 if not isinstance(level, dict):
  break
 for j in range(i, len(chars)):
  level[chars[j]] = {}
  last_level, last_char = level, chars[j]
  level = level[chars[j]]
 last_level[last_char] = {self.delimit: 0}
 break
  if i == len(chars) - 1:
level[self.delimit] = 0
 def parse(self, path):
  with open(path,encoding='UTF-8') as f:
for keyword in f:
 self.add(keyword.strip())
 def filter(self, message, repl="*"):
  if not isinstance(message, str):
message = message.decode('utf-8')
  message = message.lower()
  ret = []
  start = 0
  while start < len(message):
level = self.keyword_chains
step_ins = 0
for char in message[start:]:
 if char in level:
  step_ins += 1
  if self.delimit not in level[char]:level = level[char]
  else:ret.append(repl * step_ins)start += step_ins - 1break
 else:
  ret.append(message[start])
  break
else:
 ret.append(message[start])
start += 1
  return ''.join(ret)